Linux probably doesn't have the programs you want, but it does usually have subtitutes which work just fine (MSN -> Pidgin is one such good example)
If the only reason your wife likes AOL is for the email address, that is available elsewhere. Just google AOL mail. I'm not sure if you can transmit an existing AOL account into a pure-email account, but I can't see why you wouldn't. If she likes using the Instant Messanger, that is available through Pidgin as well. Pidgin works almost identically to AIM.
What NAI said, though, is absolutely true. Ubuntu is great if it works properly on your hardware "out-of-the-box", but a nightmare to troubleshoot. That said, it works fine on most computers, and there's a much better chance of it working if you're on a desktop. I used it for about a year, and then had to switch versions of linux because (after an update) my computer started freezing every time it tried to wake up from suspend, and I had no idea why. The screen just started flashing random static-y looking colors. However, I'm using a laptop and my hardware is kind of tricky.
I second peppermint's diagnosis. Get some sort of antivirus (NAI's suggestion of Avast is a good one) and look around for the option to run a boot-up scan. My intuition thinks that this will solve your problem. If that fails, then try a rescue cd. If that fails, then tell your wife to use AOL mail, teach her firefox, and give Ubuntu a shot.
Some other thoughts worth mentioning, because I haven't seen them yet.
1. You can try Ubuntu without installing it, if you go to their site, download it, and burn it onto a cd. When your computer starts, look for something that says "hit f12 [or some other f-number] to [do something]" (my memory's foggy... but you won't hurt anything if you hit the button and then just exit whatever menu first pops up), and tell it to boot from cd. That should put you in a fully functional ubuntu (although it will be a lot slower than it would if it were actually installed), so you can test whether it works with your hardware beforehand, and see whether or not you like it. If it seems to work fine (make sure you have sound, it works with your printer, flash-programs work through firefox, etc), then it's safe to install for real.
and
2. You can probably call up either Microsoft or the place where you bought your computer and get them to send you install disks. I didn't know this, but when I was having trouble with my laptop I called up Dell, and since my computer also came with Windows installed, they sent me the install disks so that I could wipe it if I needed to. It was still within warrantee, so that might have something to do with it... but either way, it's worth a try for you. Also, most computers that come pre-installed with windows, but have no install disks, have a separate piece of the hard drive with all the "windows installer" stuff which is (I think?) protected from viruses. You might want to check to see if that's the type of computer you have, because you might not need install disks in order to reinstall it.
less importantly (but still important):
3. I would not recommend going to a professional and asking them to fix it. A very cheap new computer would probably not cost too much more than getting someone to fix your current one, because they're really expensive, and to be honest, they'll most likely just erase everything and use the same Windows install disks which you could get for free to reinstall it.
