Some time ago, having installed SP3, my system went TU. 'twas something about drivers, not XP itself - you should see the peripherals I've got strapped onto this thing.
Um: what to do?
Then I remembered that in XP, if you put the CD in, one of the options is to type 'R' to repair windows. So, in with my XP with SP2, and guess what:
it wouldn't run because I'd SP3'd the system.
Nothing for it but to back up and do a clean reinstallation. Lost a lot of settings and tweaks, of course, but at least I still have a m/c that works... for now. Now then. Do I install SP3 again?