768mb budget ram (3 x 256 various manufactuers)
That's going to kill your success regardless of your proc. When overclocking, not only do you want to avoid generic RAM, but having different brands will put a crimp in your OCing. You want high quality sticks (read: Corsair XMS, OCZ Gold and/or EL, Crucial Ballistix, Kingston HyperX, or Mushkin hi-performance). Also, you'll generally have better success with fewer sticks installed. For example, you'll likely get a better OC with 2x512mb sticks vs 4x256mb, even though both come out to 1g. Lastly, I would advise looking for PC3200 as a minimum. You want headroom.
Moving on to your motherboard, I read a user review online that stated there's no AGP/PCI lock. If that's the case, you're going to be overclocking those as well, so be aware. If there's no lock, I wouldn't put the risk on whatever components you have installed.
With the proc, your success is going to be limited. If it's a Palomino, I would expect a stable overclock to be under 100MHz.
Lastly, cost. Buying new RAM (especially enthusiast RAM) is not cheap, considering your proc isn't going to give stellar OCs. XPs are so inexpensive these days, if you need a performance boost you'd be better off splurging for a new processor. However, if your goal is simply to get into overclocking and get your feet wet, buying better RAM may very well be worth it to you, as that's subjective. Personally, I wouldn't do it unless I was going to be upgrading my platform as well.