Primary Computer Service, Inc.

Serving Houston Since 1984!


Book Service Call Now


Dell BIOS Password


Last week I ran into a very annoying problem involving a Dell laptop I bought from eBay. Everything seemed OK at first, but when I tried to enable Intel's virtualization technology in the system's BIOS, I realized the entire BIOS had been password protected. Aggravated, I emailed the seller and kindly asked him to provide the password. After receiving his response, I was way more than aggravated. After deciphering his nearly incomprehensibly broken English, I realized that he neither had the password, nor would be willing to refund the item. Mind you, I hadn't even asked for a refund. Now I was left with a password protected BIOS and would have to deal with it myself.
At first, I thought it would be a minor inconvenience. An old trick to reset BIOS passwords is to locate, remove, and reinstall the CMOS battery on the motherboard. This clears the settings in BIOS to the factory defaults, including the passwords. I acquired the laptop's schematics from Dell and spent four hours disassembling the laptop, unplugging the CMOS battery, plugging it back in, and reassembling the laptop. To my horror, the password was still set upon turning the computer back on. It appears about a decade ago, Dell wised up and began storing BIOS passwords in a small flash chip on the motherboard. This is especially true in their laptops and I assume it was done because laptops have a high theft rate.
Researching the topic online showed that Dell assigned an unique master password to each individual computer BIOS based upon the computer's service tag. So, an alternative route would be to contact Dell, claim ownership of the laptop, wait for the claim to go through, then request the master password Dell generated for this specific computer. This wasn't an ideal solution since this process would take several weeks or even months at the minimum.

During my research I noticed that several eBay sellers were providing these master passwords for a small fee. Obviously, this meant that the means to generate these codes oneself was available somewhere on the internet. That's when I ran across some source code created by Russian hacker hpgl who found the algorithm Dell was using to generate these master passwords for the 595b and 2a7b-type BIOS. You can find the code below:
#include <stdio.h>
#include <string.h>
#include <time.h>
#define mystr "My own utility. Copyright (C) 2007-2010 hpgl, Russia"
#define allow595B
#define allowA95B
#define allow2A7B
#define fSVCTAG 0
#define fHDDSN 1
#define fHDDold 2
#define t595B 0
#define tD35B 1
#define tA95B 2
#define t2A7B 3
#ifdef allow595B
#define f595B
#ifdef allowA95B
#define f595B
#ifdef allow2A7B
#define f595B
char bSuffix[]="595BD35BA95B2A7B";
char scancods[]="\00\0331234567890-=\010\011qwertyuiop[]\015\377asdfghjkl;'`\377\\zxcvbnm,./";
char encscans[]={0x05,0x10,0x13,0x09,0x32,0x03,0x25,0x11,0x1F,0x17,0x06,0x15, \
                 0x30,0x19,0x26,0x22,0x0A,0x02,0x2C,0x2F,0x16,0x14,0x07,0x18, \
#ifdef allow2A7B
char chartabl2A7B[72]="012345679abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ0";
unsigned int MD5magic[64]={
0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391};
unsigned char inData[23],outData[16];
char buf1output[32], buf1input[20];
char bug4;
void calcsuffix(char bfunc, char btype, char *outbuf);
void initData(void) {
	*(int *)(&outData[0]) =0x67452301;
	*(int *)(&outData[4]) =0xEFCDAB89;
	*(int *)(&outData[8]) =0x98BADCFE;
	*(int *)(&outData[12])=0x10325476;
typedef int (encfuncT1) (int num1, int num2, int num3);
#ifdef f595B
int enc0F2(int num1, int num2, int num3) {return (((~num3 ^ num2) & num1) ^ ~num3);}
int enc0F4(int num1, int num2, int num3) {return (( ~num2 ^ num1) ^ num3); }
int enc0F5(int num1, int num2, int num3) {return (( ~num1 | ~num3) ^ num2); }
int enc1F2(int num1, int num2, int num3) {return ((( num3 ^ num2) & num1) ^ num3);}
int enc1F4(int num1, int num2, int num3) {return (( num2 ^ num1) ^ num3); }
int enc1F5(int num1, int num2, int num3) {return (( num1 | ~num3) ^ num2); }
int encF3 (int num1, int num2, int num3) {return ((( num1 ^ num2) & num3) ^ num2);}
typedef int (encfuncT2)(encfuncT1 func, int num1, int num2, int num3, int key);
int enc1F1 (encfuncT1 func, int num1, int num2, int num3, int key)
	return func(num1,num2,num3)+key;
#ifdef f595B
int enc0F1 (encfuncT1 func, int num1, int num2, int num3, int key)
	return func(num1,num2,num3)-key;
unsigned int rol(unsigned int t, int bitsrot)
	return (t >> (32-bitsrot)) | (t << bitsrot);
void blockEncodeF(int *outdata, int *encblock, encfuncT2 func1,
                  encfuncT1 func2, encfuncT1 func3, encfuncT1 func4, encfuncT1 func5 )
	char S[4][4] = {{ 7, 12, 17, 22 },{ 5, 9, 14, 20 },{ 4, 11, 16, 23 },{ 6, 10, 15, 21 }};
	int A,B,C,D,t,i;
	for (i=0;i<64;i++) { 		t=MD5magic[i]; 		switch (i>>4) {
			case 0: t=A+func1(func2,B,C,D, t+encblock[(i) & 15]); break;
			case 1: t=A+func1(func3,B,C,D, t+encblock[(i*5+1) & 15]); break;
			case 2: t=A+func1(func4,B,C,D, t+encblock[(i*3+5) & 15]); break;
			case 3: t=A+func1(func5,B,C,D, t+encblock[(i*7) & 15]); break;
		A=D; D=C; C=B; B+=rol(t,S[i>>4][i&3]);
void blockEncode(char *outdata, int *encblock, char btype) {
	if (btype==tD35B)
		blockEncodeF((int *)outdata,encblock,enc1F1,enc1F2,encF3,enc1F4,enc1F5);
#ifdef f595B
		blockEncodeF((int *)outdata,encblock,enc0F1,enc0F2,encF3,enc0F4,enc0F5);
void encode(char *inbuf,int cnt,char btype) {
	int encBlock[16];
	char *ptr;
	ptr=&((char *)encBlock)[cnt];
	encBlock[16-2]=((unsigned int)cnt << 3);
void psw(char bfunc, char btype, char *outbuf) {
	int cnt,i,lenpsw,r;
	if (bfunc==fHDDold) {
//		calcsuffix(bfunc,btype,outbuf);
		for (cnt=0;cnt<8;cnt++) 			outbuf[cnt]= scancods[ outbuf[cnt] ]; 	} else { 		memset(inData,0,sizeof(inData)); 		if (bfunc==fSVCTAG) cnt=7; 		else cnt=11; 		if ((bfunc==fHDDSN) && (btype==tA95B)) 			memcpy(inData,&buf1input[3],cnt-3); 		else 			memcpy(inData,buf1input,cnt); 		if (btype==t595B) memcpy(&inData[cnt],&bSuffix[0],4); else 		if (btype==tD35B) memcpy(&inData[cnt],&bSuffix[4],4); else 		if (btype==tA95B) memcpy(&inData[cnt],&bSuffix[0],4); else 		if (btype==t2A7B) memcpy(&inData[cnt],&bSuffix[12],4); 		cnt += 4; 		inData[cnt] = inData[4] & 0x1F; 		inData[cnt+1] = ((inData[4] >> 5) | (((inData[3] >> 5) | (inData[3] << 3)) & 0xF1) & 0x1F); 		inData[cnt+2] = ((inData[3] >> 2) & 0x1F);
		inData[cnt+3] = (inData[3] >> 7) | ((inData[2] << 1) & 0x1F); 		inData[cnt+4] = (inData[2] >> 4) | ((inData[1] << 4) & 0x1F); 		inData[cnt+5] = (inData[1] >> 1) & 0x1F;
		inData[cnt+6] = (inData[1] >> 6) | ((inData[0] << 2) & 0x1F); 		inData[cnt+7] = (inData[0] >> 3) & 0x1F;
		for (i=cnt;i<8+cnt;i++) {
			r = 0xAA;
			if (inData[i] & 1)
				r ^= inData[4];
			if (inData[i] & 2)
				r ^= inData[3];
			if (inData[i] & 4)
				r ^= inData[2];
			if (inData[i] & 8)
				r ^= inData[1];
			if (inData[i] & 16)
				r ^= inData[0];
			inData[i] = encscans[r % sizeof(encscans)];
		cnt = 23;
		r = outData[0] % 9;
		lenpsw = 0;
		for (cnt=0;cnt<16;cnt++) {
			if ((r <= cnt) && (lenpsw<8)) { 				buf1output[lenpsw++] = scancods[encscans[outData[cnt] % sizeof(encscans)]]; 			} 		} 	} } int main(int argc, char *argv[]) { 	unsigned char len,len1,bfunc,eol=1,echo=0, *minus,s2[20]; 	signed char btype; int argn=0; 	if (argc>1)
	if (!echo)
		fputs("" mystr "\n" \
		  "Short service tag should be right padded with '*' up to length 7 chars\n" \
		  "HDD serial number is right 11 chars from real HDDSerNum left padded with '*'\n" \
		  "Some BIOSes has left pad HDD serial number with spaces instead '*'\n",stdout);
	while (!feof(stdin)) {
		if ((argc<=1) && argn) break; 		fputs("Input: #",stdout); 		if (argc>1) {
		else {
			if (!eol) while (!feof(stdin) && (fgetc(stdin)!='\n')); eol=0;
			if (fgets(buf1input,16+1+1,stdin)==NULL) {
				if (echo) fputs("\n",stdout);
		if (len && (buf1input[len-1]=='\n')) {len--;eol=1;buf1input[len]=0;}
		if (echo) {fputs(buf1input,stdout);fputs("\n",stdout);}
		if (len==11) {
			if (minus!=NULL) {
				fputs("- Incorrect input\n",stdout);
			fputs("By HDD serial number for older BIOS: ",stdout);
		} else {
			if (len==0) break;
			if (minus==NULL) {
				fputs("- No BIOS type found in input string, must be followed by -595B and other registered\n",stdout);
			len1=minus-(unsigned char*)buf1input;
#ifdef allow595B
			if (strncmp(&buf1input[len1+1],&bSuffix[0],4)==0) btype=t595B;
			if (strncmp(&buf1input[len1+1],&bSuffix[4],4)==0) btype=tD35B;
#ifdef allowA95B
			if (strncmp(&buf1input[len1+1],&bSuffix[8],4)==0) btype=tA95B;
#ifdef allow2A7B
			if (strncmp(&buf1input[len1+1],&bSuffix[12],4)==0) btype=t2A7B;
			if (btype<0) {
				fputs("- Invalid service tag in input string, allowed only -D35B and other registered\n",stdout);
			struct tm *time1; time_t timer1=time(NULL);
			strftime(s2,sizeof(s2),"%d.%m.%Y %H:%M",time1);
			fputs(" DELL ",stdout);
			if (len1==7) {
				fputs("service tag: ",stdout);
			} else
			if (len1==11) {
				fputs("HDD serial number: ",stdout);
			else {
				fputs("- Incorrect input, must be 7 chars service tag or 11 chars HDD serial number\n",stdout);
		fputs(" password: ",stdout);
		if (bug4) fputs(" !bug4 warning - password may not work!",stdout);
		if (btype==t595B) if (bfunc==fSVCTAG) { //to check if A95B bug
			char mpw1[20];
			if (strcmp(mpw1,buf1output)!=0) {
				fputs(" passwordA95B: ",stdout);
	return 0;


I entered my service tag into the software, and out popped some random letters and numbers. I tried the generated characters in the BIOS and it worked! Good luck!


Primary Computer Service, Inc.
Copyright Ⓒ 2020 [Primary Computer Service, Inc]. All rights reserved.