|It could be a faulty hard drive that's corrupted the operating system's boot files.|
test the drive with the drive manufacturer's own diagnostic software for DOS. The links are here: http://www.tacktech.com/display.cfm...
The download for the DOS version is an ISO file from which you must make a CD using IMGBurn from here: http://filehippo.com/download_imgburn/
When you've made the CD, boot your Acer laptop from that CD to test the hard drive.
if the test does not find any fault with the drive, you just need to re-install Windows on it or use the Acer eRecovery process to return it to it's factory pre-installation state.