|If it's just a Windows password, usually the Windows Adminstrator user has no password. |
Remove any bootable CD or DVD in the optical drive.
Press F8 repeatedly while booting, do not hold down the key, and when the Windows boot choices menu (white text on a black screen) appears, choose Safe mode or Safe mode with networking.
(Some laptops also use F8 for something else such as a boot devices choices menu - if you see that, exit it and immediately repeatedly press F8 again to get the Windows boot choices menu.)
You will see the screen fill with lines , then it will stay the same for a while, then you'll see a Logon screen - choose Administrator, just press enter when the password box appears.
If that works, either use System Restore to go forward in time to when there was no password, or delete the user you do not know the password for in Control Panel.
Note that if you delete a user ALL of the personal stuff for that user that's in C:\Documents and Settings\(that user)\all the users files and folders, and the (that user) folder are deleted too - that includes everything in My Documents , My Pictures, My Music, etc. for that user and the user's personal email stuff if that applies, and at least some of the users personal settings and files for programs that make entries there. .