Hi Stu,
I recently (January) upgraded from Vista to W7. I too run Firefox (4.0). I had some 'fun' with the comp last year when the mother board packed up, and decided on the upgrade after getting that fixed. No probs with the upgrade. I got it from the MS website, both download and CD. Mind you, at my download rate, it was almost as quick waiting for the CD to arrive.
Tried 32 bit first, that went OK, so swapped for 64 bit. Both included in download/CD. I have since upped the RAM from 2 to 4 gig, but even with 2 it ran smoother and faster than with Vista.
One thing you might like to trry first though. A couple of years back I was having similar problems to those you mention. I went as far as trying Ubuntu. End of problems, but it did bring a few of its own, mainly relating to which applications would run on it. Still, I was willing to sort it. Then a friend mentioned something on a web site I use. Actually, he'd been preaching it for a few months, so I gave it a go.
Up to that point, I'd been using 'Avira' anti-virus. Good stuff, no problems, except the comp gradually slowing down. So on Tim's recommendation, I tried 'Cloud' AV.
Instant speed up of comp. I was surprised, but it went back to working as it had when I first bought it eighteen months earlier.
All I can think of is that, having Avira set to update every day, it had accumulated so many update files that it was slowing the comp down just running through them. Cloud doesn't have up-date files, it's constantly updated. I'd recommend you try it. Just click the link in my sig, download, and leave it alone to do its job. It found three things that both Avira and the famous/infamous Norton had missed. Switch your current AV off, but don't get rid, just in case you aren't happy with Cloud.
Otherwise, as I say, upgrade to W7 is good. Just to mention, as well as Firefox 4.0, I also run Thunderbird (email) and Open Office.
Cheers,
Dave.
