Are you on about a User password when you get to the login screen, or a Bios password?
If bios, try goin to your manufacturers website and see if they have got a Backdoor BIOS Password.The backdoor password is a BIOS password that works, no matter what the user sets the BIOS password to.
Here are a list of passwords for different Bios:
AMI Backdoor BIOS Passwords
Reported AMI backdoor BIOS passwords include A.M.I., AAAMMMIII, AMI?SW , AMI_SW, BIOS, CONDO, HEWITT RAND, LKWPETER, MI, and PASSWORD.
Award Backdoor BIOS Passwords
One reported Award backdoor BIOS password is eight spaces. Other reported Award backdoor BIOS passwords include 01322222, 589589, 589721, 595595, 598598 , ALFAROME, ALLY, ALLy, aLLY, aLLy, aPAf, award, AWARD PW, AWARD SW, AWARD?SW, AWARD_PW, AWARD_SW, AWKWARD, awkward, BIOSTAR, CONCAT, CONDO, Condo, condo, d8on, djonet, HLT, J256, J262, j262, j322, j332, J64, KDD, LKWPETER, Lkwpeter, PINT, pint, SER, SKY_FOX, SYXZ, syxz, TTPTHA, ZAAAADA, ZAAADA, ZBAAACA, and ZJAAADC.
Phoenix Backdoor BIOS Passwords
Reported Phoenix BIOS backdoor passwords include BIOS, CMOS, phoenix, and PHOENIX.
Backdoor BIOS Passwords from Other Manufacturers
Remember that what you see listed may not be the actual backdoor BIOS password, this BIOS password may simply have the same checksum as the real backdoor BIOS password. For Award BIOS, this checksum is stored at F000:EC60.
Or you can try and reset Bios, which will put the password back to default. Do this by either taking the cmos battery out for about 10 mins, or moving the jumper on the motherboard (if it has one) It should say clr_cmos. This is the quicker way which will take about 30 secs.
Regards Jase