It's difficult to give advice on this subject as it can be used by thieves but I'll try to give legal advice.
If it simply STOPS at the login screen and the password doesn't work you basically have these legal options that I'm aware of:
1) contact Microsoft and see if they can resolve your situation
2) contact the computer builder and see if they can resolve your situation
3) reinstall Windows from scratch (you'll lose anything on that drive). If it's a pre-built system you MIGHT be able to get copies of Windows on disc for your system. Also, if it's pre-built there's likely a hidden partition on the main drive that you can access by pressing one of the F-keys on bootup to start a RESTORE. Again, that will replace your current version of Windows.
You can also try Googling "windows password recovery" which may provide options but I'm not comfortable recommending anything further.