|Following on from riider's suggestion...|
If you boot up with a Linux dvd you can usually access the hard drive and safely copy "all" your personal stuff to external storage. Typically this is to dvd but an external hard drive is equally viable (and if possible wise to use both). Having done that you can then more easily and safely set about recovering the system to a working state; and riider's link does suggest an option or three that may do it...
You can download a free ISO for Ubuntu here:
Save it burn to a dvd; boot up with the dvd. If the system boots OK with that Linux dvd then it more or less confirms the actual kit is OK, and the problem as exists is within the current installed (Windows) OS.