Anyways, I told the OP in a PM the easiest way I know to reinstall XP, and promised to tell him other things he should do to “harden” it.
I already mentioned BitDefender. I would also recommend installing Malwarebytes Anti-Exploit. This is a differnet program from Anti-Malware, and it just hardens other applications, particularly web browsers.
I would not use Internet Explorer on XP, since you’re stuck with version 8. Firefox and Chrome are fine. But if you really want to harden them, I’d run them with Sandboxie. This will allow you to completely segregate your browser from the rest of your OS. Install your browsers and get all your addons before using it.
If you use your web browser to download files from untrusted locations, test them in the sandbox first. You may even want to use a separate one, so you can completely wipe it if there’s a problem. Only take trusted apps outside the sandbox. Read the documentation for more info on how to do that.
As for browser addons, I generally recommend Adblock Plus for security reasons. It is the least obtrusive way to block most third party Flash. Ads are generally where the malware comes from on any decent site. Even if you plan on viewing ads in some places, you should use it and just shut it off on those sites.
Another option would be to use Flashblock or to set Flash on “Ask to Activate” in Firefox’s settings. This is more intrusive, but has the advantage even more Flash content, including Flash content that belongs to the site in question. This isn’t just a security advantage, but also a performance one. Flash is poorly optimized and having multiple bits of flash content on a page can be overwhelming. I personally use it and Adblock Plus together.
To answer the question asked earlier upthread, as long as security programs and current browsers support XP, I don’t think it’s too dangerous to use. As long as you practice good computer hygiene, you can use it, even if it’s not ideal from a security perspective. If my netbook hadn’t coincidentally given out around the time for the switchover, I’d still be using XP myself.
I just didn’t give this advice before because I think it’s a shame to leave Linux for the problems the OP is having, and hoped he could get it worked out to his satisfaction.