See if you can boot into Safe Mode
with networking to install, update and run Malwarebytes
If you can't enter Safe Modes, then download and burn to CD or write to flash stick, then boot and run a full scan with Microsoft Standalone System Sweeper
Next Boot the Windows 7 DVD Repair console (on second screen) or Repair CD to run Startup Repair
Startup Repair should automate System Restore and System File checker, but if it fails run them separately from the Repair tools list: SFC -SCANNOW Run in Command Prompt at Boot
You can copy out your files using DVD/Repair CD: Copy & Paste - in Windows Recovery Console
Then run full Factory Recovery from partition first, saving Recovery disks as backup, or clean reinstall using Windows 7 DVD. If you will at least tell us your computer make/model we can help you further with these choices.