The A64's are also great 32bit processors, not to mention the huge increase in memory bandwidth since they dropped the NB and now have an ondie memory controller so you're completely looking at it in the wrong aspect.
256mb doesn't mean it's an Ultra card, it just means it has 256mb but it's not a waste because it would still perform better than a 5600 with only 128mb.
There is no such thing as
wouldnt oc the gfx card though not strong enough
Aspire so I don't know why you said that. I overclocked my Gf2 MX 32mb card before.....you OC whatever you can OC as simple as that so go for it Him.
The best cooling solution you can do is water cooling, next up from that would be chilled water cooling which involves taking apart an AC unit or using a peltier which I'm not going to go into as you could just google that and get more results.
The dude who got 7.2GHz was a guy named Fugger and holds the world record for that at xtremesystems.org he had a triple cascade phase change unit he built himself and he only got that in the BIOS, not windows..got like 6.7GHz or so within windows.......point is that's not even close to a possibility for you.
2.4GHz prescott you'd need some mighty damn good cold temps to get that sucker to 3GHz and beyond.
An AC unit pouring into the side of your case technically would work but would be mighty expensive for the electric bill.