This is the reinstallation procedure I have used on Gateway and e-machines before and it worked. Maybe you want to try it:
1. Copy all your own files and folders to an external storage(Disc, USB stick even SD card)
2. Shut the PC off
3. Turn the PC back on and keep hitting the F8 key repeatedly until theAdvanced Boot Option Screen appears
4. Click "Repair Your Computer" –if you are not already on it, use theup and down arrows to maneuver to it and then press ENTER
5. Next you have to pick your country and click OK
6. On the "System Recovery Options Screen" click "RestoreApplication" (last option)
7. Follow the on-screen instructions
8. When prompted, click on "Full Factory Recovery"
9. Click "Next"
10. Click "Yes"
11. Go and have a cup of coffee - don't touch anything - for a while it seemslike nothing is happening
12. After many minutes, recovery will complete and you click "Finish"