(not direct reply to scooby, but to all)
It staggers me how many people replied to this question and talked absolute crap about it being ram, how dual channel ram would give a mega boost, and then moved onto it being the hard drive. I can't believe it took a 8 posts before somebody actually talked sense (thankyou ape) and got onto the subject of (shock horror) graphics card drivers for what was fundementally a graphics issue.
Firstly I would like to state that apes comments of approx 3-5% performance increase with dual channel over single are absolutely correct. I have run several systems with both setups and the differences are negligable, and as ape states this has been born out in numerous reviews by tech sites. A few select apps have been shown to gain about 10% from dual channel but these are very much the exception.
Also, what the hell are you guys doing going on about 512mb bottlenecking his system?? Have you got any idea at all how a computer or Windows XP works????!!!!!!! In the real world 512mb of ram bottlenecks absolutely nothing except large ram intensive apps such as video editing, graphics/3D editing, photo editing, a select few games such as Battelfield 2 and COD2 and absolutely NO benchmark programs ever made. 3Dmark06 runs exactly the same on 512mb as it does on 1gb, so 05 will certainly not require any more. Whislt it is all great and fine for enthusiasts to have gigs of ram, you don't actually need it unless except for high mem usage apps, or to get an extra couple of percent difference in XP performance because that is all it does. Not 20% as suggested by many here, but about 2%, and that is a fact again shown by numerous tech sites.
Maybe before some of you guys post next time you should first get to know what the hell you are talking about and stop giving extremely poor, and in this case utterly wrong advice. I cant believe that out of 16 people only 3 have talked any sense.