There is a crucial file missing and it's not obvious whitch one. It must be restored, but you can't just copy it back, you need to reinstall Windows.
Get a live CD and boot from it.
---> VITAL STEP!!!!!
Copy your files and documents to an external drive.
Reinstall Windows. Try the "Repair installation" option if it's available. That option will atempt to restore missing and damaged files while atempting to preserve your data.
Electro, March 2012
