Moose was correct - who the heck is your ISP. With advice like that, it's time to stage a anti-ISP campaign. That's more than negligent, that's criminal as far as I am concerned (as a successful ISP for 11 years, my company/customer service personel had better NOT give that kind of BS advice) the first step is always to back up data and reformat the hard drive..
If that doesn't work - replace the hard drive.

if THAT doesn't work, your machine was toast to begin with - and you are out less than $100 bux for a drive you can put in the new machine.

The only reasons to change to a new machine is if you want to move to new technology, you want a significantly faster processor, or (it sometimes happens, but rarely) the machine actually dies