if shitty windows is having trouble backing up your files download knoppix live iso
install it to a usb an set your pc's bios to usb boot before hard drive (can also burn it to a cd and set dvd/cd drive before hd)
this is a live linux operating system that runs of usb/disc use that to acess your c;/ drive then copy your data
then format your hard drive an have a clean win7 to work with
personally i hate windows
V-iruses
I-ntruders
S-pyware
T-rojans
A-dware
download ubuntu studio live disc an try it out for a while
p.s. live discs will come as a .iso file an are a full linux operating system that you can run from cd/dvds, usbs an external hard drive etc make sure you put disc/usb in a boot
these will not affect your install operating system so you can run em as you wish, if you cant get on with it just shutdown an remove the cd/usb next time you turn you comp on it'll go back to windows as if nothings happened
hope this helps