Firstly, antivirus applications make your PC slower so using a few of them isn't a good thing. If your pc is slow after you reformat there is something wrong. Either upgrade hardware or get a new pc.
All you need is Ubuntu, my 5 years old machine, AMD duron run as fast as my 2 years old windows machine
1) no question you need more than 512MB of the RAM...1G min, I don't care if all you do is the google and the solitaire Win alone will chew 1/2 of that 512 easily....then the 2 progs you mentioned, another 50-100MB...I'm no math major but that's cutting it awfully close to 512MB right there. 2) Has the inside of the case ever been cleaned (blown out, dust removed, etc.) Dust is a speed killer, it can cause parts to heat up as well. My old AMD XP2600+ used to crawl big time when it got too dusty up in there. but yeah, alternatively if you've got a big bankroll upgrade that mutha
yeah, if it lags a** after a fresh install, there are other forces @ work...replace the gerbil wheel, reseat the vacuum tubes...
Its not true buddy. In my opinion, if you have enough funds then replace the motherboard and processor. Get new fresh pieces and enjoy the speed. You have enjoyed its service of two years. Now new advanced processors are out. Go for them.