It sounds like the boot sector on your hard drive has an error. Who is the manufacturer for the hard drive? Hitachi, Samsung, WD, Seagate? Check their web site for a diagnostic utility and see if it finds any errors. Also, run Windows CHKDSK to see if it finds any errors that can be fixed. Did you make a back up of the O/S on CDs? If worst comes to worst, you would have to replace the hard drive and buy the recovery CD from Acer for about $20 plus shipping. It would be a good idea to back up your personal files ASAP because it sounds like your drive is failing. You should do that before you run CHKDSK or the manufacturer's diagnostic utility. Good luck.
