Yes my problem started when I tried to download a new login screen. Well I did just that and then installed it then I had to reboot perfect so far. Now comes the moment of truth to see if the login screen will work nope nothing just a black screen no where to login in at. So I decided to reboot in safe mode I did that and it worked I logged in but I don't know how to reset the login screen or what file it would be stored in. I need to get it open I'm a student and my work is on my com and I can't get into it.

K. Not a lot of detail there... Lessee, some logon changers alter boot.ini to start their logon screen, others replace the bitmaps in logonui.exe, some replace logonui, some just get called by a Run key.
So, what logon changer are you using?

It might not be a good idea to go messing around the system32 files...especially if you're unsure of how to make and undo changes. Rather, I'd boot into safe mode, copy all data to DVD or flash drive, and reinstall windows. Your login screen won't be flashy, but it will work, and you will still have your files.