VIA recommends that the drivers be installed for all chipsets for increased stability and performance.
But then there is the old adage; If it ain't broke ... don't fix it. I would say that you'll have to determine whether or not you need the drivers by ascertaining how well the system is actually running.
There are benchmarking programs and online sites that can help you with this, such as <A HREF="http://www.reactorcritical.com/download.shtml#2300" target="_new">SiSoft Sandra</A> and <A HREF="http://pcpitstop.com/" target="_new">PC Pitstop</A>.
Well, aside from a good philosphy above (per Toejam), I installed the latest 4-in-1 drivers (for a kt133 chipset) and could see a noticable increase in speed... particularly logon.. but I kept getting the "serious error" message prior to... but now its pretty much gone..
Well now that I have the resolution problem fixed (thanks TJ), everything seems to be running very smooth so I dont think I am gonna install the 4-in-1's yet. I scored 3554 on 3Dmark2001 under win98se. I will benchmark it again with XP and see what it looks like. I am already putting my poor little Gforce2 to the limit.