Unfortunately, you've given us NO INFORMATION about your computer such as the operating system, make and model, age of the computer, etc. The more information you give us, the better informed our answers will be.

Most newer computers can use System Restore from Safe Mode if you can't reach it in "normal" Windows. For example in Windows XP, after restarting in Safe Mode, click on Start-All Programs-Accessories-System Tools-System Restore. When that opens, click on the "Restore my computer to an earlier time" and at the next "Calendar" page, select a bold date before the problem with the computer took place. Click on "Next", then follow the prompts to restart the computer and go back to a date when things were good..

Hope this helps.