firstly get some more ram, its dirt cheap so bin your 64mb of ram its worthless nowadays and get a stick of 256mb ( you can probably get it for £25 from a pc show)
you need to look at your mobo's website site to see how much you upgrade your processor to, sometimes they have BIOS updates which will give that bit extra, with you having a 400mhz cpu a faster processor for your board will be cheap,
alternatively you could try over clocking your cpu through your jumper settings/bios setting but make sure you stick a few more fans in your pc coz overclocking causes your cpu to process more info at a faster rate and subsequently makes it hotter, a cyclone fan would do the job.
i don't know what your financial situation is so if your on a limited budget get a decent video card, the geforce 2 mx are at a good price
LS's Tip of the weekESSENTIAL OILS aren't essential unless you're an engine, a gearbox or a twat