If you can log into the computer, go to Start>All Programs>Accessories>SysTools>SysRestore. Restore back to the farthest date the computer can go. Also, you can use the OS installation disc to repair your copy of Windows, or any Acer maintenance discs that came with your computer.
1. Check the plug on the drive for damage, dirt or dust
2. Clean out the USB ports on the computers using a can of CO2
3. Open it and inspect the drive thoroughly for damage (Not recommended)
4. get a new one
To prevent this from happening again:
1. Unplug it when not in use otherwise it will...