Actually, we do frown on posting recommendations of Ophcrack or anything password hacking related, in case we're helping people hack other folks' systems.
I'll leave it here this time because there is a proper Registry tweak that puts this right. Go into the Registry by typing regedit in the Run box and pressing Enter. First, select Export from the File menu and note the name and location of the backup you're about to create.
Then, navigate through the Registry to this key:-
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
Find the long filename and make sure it's yours and not your granddaughter's. You need the one with no filename extension and when you find it, right click and rename it with the extension .old. The find the same filename but with the extension of .bak and rename that so it has no extension at all.
Once you've done that, leave the Registry from the File>Exit menu and restart the computer. You should then find your Profile is back intact.