If you know the password you can set it up so that when it boots a password is not needed. If you do not have the password at all. Then use a crack program or reinstall, or see below.
Use LNX-BBC.
http://www.lnx-bbc.org/You can boot on nearly any and all machines and access any hardrive with this Linux OS, reads most file system formats. It has over a thousand programs to work with. It is small enough to fit on a business card cd. Boots from the CD. When it boots it is read only so you do not have to worry about overwritiing data or corrupting anything. You have to configure it to get write access, instructions are included.
You can crack or change any windoze version and or windoze password with this OS.
You do not need write access to crack the password. Simply find it, use "johntheripper" or one of the other crack programs. There a number of crack programs available on the cd.
If you are not able to boot into GUI then boot into the command line, it hangs with some of the newer graphics cards.
The Linux revolution will overtake the windoze monopoly in the near future. Long live freedom.
Have Fun!!
Vulgar