Drivers are strange things. I've tried most drivers (official, detonator, Omega) in my rig over the last six months.
Firstly, don't necesarily take marcl's advice. If you're confident that you know what your doing, there's absolutely no reason why you shouldn't upgrade - that why they're there.
Secondly, different driver creators have different ways of upgrading so makesure you read their installation guide CAREFULLY.
Next, SPEED IS NOT EVERYTHING. I'm using the new Omega drivers - on my system I can get detonators that are quicker but 3-5 fsp increase but it isn't worth it if you can see the difference (loss) in visual and texure quality.
Tweaks and Gizmo's to increase your performance are well worth trying too although be careful onceagain which drivers you use them with (i.e. Omega drivers ARE tweaked original drivers so if you fart around with them - you loose the point in having them in the first place).
Finally, check out some "tweaker sites". These guys tend to be a bit anoraky but as long as you realise that you don't know as much as them and they're old hands at it, you can try some of their simpler advice.
Jackie
(P4 1500hz, Geforce3 ti200, Win98SE, 256 DDR, 60Gb HDD)
....................I quite like this now.