'Missing' programs

[drgnfireinferno]

So I'm at a conundrum here, I shutdown my computer one night and wake up in the morning to find it's been the target of something. Half the folders in my Program Files list seem to be missing, and searching I can't locate them. I'm more so assuming they were deleted or some such thing. I assumed it to be a virus at first, but after doing a full scan of my system there isn't a single virus on it (not bad for someone who's neglected to get an anti-virus program for a year and a half. ) So my idea of it being a virus is shot. I'm under an impression that it could be part of a hacking program which has tried to access my network, but seemingly given up after I kept saying no (though it's possibly my computer and technologically impaired mother could of allowed it access, though she claims to not have, despite not knowing what I'm talking about.)

So anywho's anyone have some idea as to what it hitting my system and how to best throw it out?

Ah yes I forgot to mention I had a few gig suddenly shoot up on free space, which made me a bit suspicious.

As for that whole hacking program, on my firewall I just kept getting a request for some program to access my network, I promptly refused and would see another pop up stating 'Program Hi-jacking blocked from access to the network.', for a while it was a very consistent program for about a week every day multiple times a day it would appear and bug me (as my fire wall refuses to acknowledge the fact that I tell it to not tell me about it blocking it again and again. >.<)

But I doubt my hard drive is failing, it's only about a year and a half old, maybe slightly older, so I'm in doubt that it's that at the moment. (And I don't want to buy another 80 GB hard drive if I can help it >.>)

firstly, just because it says it hasn't found a virus doesn't mean that one isn't there. Not all virus are known by the anit-virus companies and some virus are designed to affect your anti-virus program itself.

secondly, your hard drive can fail for many different reasons, regardless of it's age. One is a power surge, which is the caulprit 98% of the time.

thirdly, alot of hackers, like the one who tried to get in your system but were stopped by your firewall, know how to get through a firewall. If they hack through your firewall you won't get that message since they are already in.

and lastly, it could be a spyware, or other malicious software. It is recomended by MANY PC technicians to have not only an anti-virus program but atleast two anti-spyware programs. I recomend Spybot and Adware which are both free to download and use. You can get them both from http://download.com.