which password screen are you talking about? is it the BIOS password screen?? if so you should be able to take out the CMOS battery and wait for about a minute. that will reset the BIOS and wipe the password.
If it is a HD password then I have not seen a way around these. the problem is that the security chip is built into the HD controller board and is not bypassable. But if you can get into the BIOS you might be able to change it from there.
If it is windows password, what version of windows is it?
If it is Windows 2000 or XP you can use ICWT – In Code We Trust. It is a bootable cd that allows you to reset the admin passwords or a password of any other account. Google it to find it on the net.