what kind of errors are being noted? If it's just crosslinked files and such, the OS (what is it?) may have a built in utility. If it's actual bad sectors, the remedy is different or not available. In worst cases, you can erase the drive with a utility from the manufacturer that will do a sector by sector surface analysis. Some can "move" unrecoverable sectors to spare ones. This process marks bad spots so they will not be made available when you partition and format the drive. One small program that's supposed to do miracles is called "Spin Rite", as I recall, but it's not free and will cost as much as today's 80 gig drives.
My son recently gave me his computer and i am cvery happy and very grateful,however there is one problem. the hard drive (c) is absolutely full of dross i.e. bits of uninstalled programs and such like. i have used registry mechanic and although it reports that i have 468 errors on my drive it will only repair 29 of them,as have a few others i have tried, therefore my question is this, can anyone recommend a good free program that will actually repair the errors as well as finding them? thank you for taking the time to read this, and for any help you may offer