I bought this machine for nearly nothing at a Wall Mart in 2008 and have been very pleased with it except for having the same issue.
This happens to my, now my daughter's, laptop once in a while. My solution has been, take the battery out, turn it over, remove the 8 or so screws holding the bottom access panel in place, disconnect the hard drive, removing it entirely from the connector, reseating the hard drive, and reversing all of the previous steps.
This solution was discovered by accident as the local Acer technician in Hong Kong also could not figure out the issue and was quoting me on a new motherboard, battery, etc. and I said no and that I would figure it out from here. He put it all back together and viola, it worked.
I have had to do this no less than twice a year since then.