Re: How to reinstall computer
Hmm, tough question.
Did you by any chance register your MSN/Hotmail/etc. account in Windows? If you did, try using that Microsoft account's username and password to log in. Also, are you sure you created specific username and password or just locked it? With some settings, Windows could show this screen even with no password set. Try using the name of your computer with the password field blank, or both blank all together.
The above is not likely, and I guess formatting is most likely the way to go. You know what, if it is not important for you to keep this current Windows installation, just format it and save yourself the trouble. There's probably a sticker somewhere on the case with the Windows Key since the computer is a brand setup. That will allow you to install any Windows of the same version mentioned on that sticker. So no worries in this part if it's confirmed.