I think the answer to your question is no it is not always the hard drive that a virus attacks , i dont think that you should rush into scrapping your PC just because of a virus attack, it has to be realy bad to do that, stop panicking and run your anti virus program several times, go to snap files .com freeware and look down the anti virus list and try different software, always remember to scan any new downloads before opening, i have had these problems just search repetedly you will beat it in the end, remember viruses are sent to try and ruin your enjoyment dont let them or it win, good luck ; alan
PS you could buy a new PC and pick up a virus the next day !!