I'd either re-install fresh or recover from a backup image.
First though see if Windows boots in SAFE mode. (Press and Hold F8 key on Windows Boot). If it does then just shut down again and try and boot normally.
If you haven't got a backup / restore program it's ALWAYS worth spending a little money on buying one. You can also make bootable media so you can restore via booting from a DVD or USB device.
Backup shouldn't take you more than 30 mins to an hour and really will get you out of a hole many many times.
In a way this is a good experience to understand why a backup program is necessary -- computers DO go wrong for all sorts of reasons --a decent backup gets you out of all sorts of messes.