Looks like some crutial file got erased from your root folder.
Get a Linux Live CD and use it to boot. You can download an image that you can burn on a CD or get one at several computer shops.
A live CD let you boot to some functional OS without making any alteration to your drives unless you explicitely do so. Great to test it or recover data from a corrupt installation.
From the linux environment, backup your data.
Reinstall Windows, or make the jump and install Linux.
Reinstall your applications.
Restor your backedup data.
Electro, August 2011
