Hey, you said that your CPU is a Pentium 4 with HT technology, yet you didn't mention anything about the GHZ rating yours has, though you said your mate has a 2.4GHZ processor. Whats yours?
Your mate also has more RAM in the system and so will be getting a boost from this since more programs will be able to run and so faster
Even though your graphics card is better than yours, honestly, the RAM on the card doesn't matter that much to speed in games, so do note that. The only time this RAM on the video card is really needed (except for the obvious stuff) is when texture caching while playing new games that need alot of textures as map sizes get bigger and more detailed, though most games use compressed textures anyway so should be fine for his 128mb card, and so the only time your mate would encounter problems would be on a really new game, running on ultra high quality with no compressed textures. This is where your 256mb card would come in handy, yet its not just this that is important while buying a card.
Also, a performance program would only really make sure memory that isn't needed is cleared from the cache and make sure that programs not needed aren't running, so even though it would give him a bit of a boost...he has a lot of RAM in the first place, so its probably not really this giving him that.
Though i shoudl note that most people survive fine with 512mb of RAM, and only if running loads of programs in the background...and you like to multitask
(like me) do you need more RAM, though if you can afford 1gig, you might gain a small boost if you do.
I hope this helps