Hi newcomer and welcome to the Tom's hardware forum.
If you can't star windows, download Hiren's boot from here and do this:
1- Boot from the CD.
2- Go to password tools
3- Select Active Password Changer
4- Scan you drives
5- Select C:, and you user
6- Uncheck and checl again the two options with the X
7- Reboot your PC and try to log in.