Without getting too techy my goldfish says that ... unlike many other hardware devices USB is supported by your operating system and not by your hardware (NO usb in DOS (you can .... but that's another story) or 95 .... USB only with extra drivers in 98 and native in 2000, XP and Vista!
The first USB mouses (mices?) and keyboards worked fine UNTILL you tried to configure the BIOS and then it all got wierd ....
(next a lot of half truths .....)
Second generation motherboards support mouse and keyboard as "legacy" devices .... so while they are USB ... the motherboard thinks they are pS2 - so they work in all conditions (probably!)
This is a long way of saying .... do it! ... delete them all .... you'll be OK .... if system locks power off/on and windows will (should) sort itself out,
This works 95% of the time ...
To be fair to the un-repair guy ...there does come a point where crash and burn is the only option if you have the recovery CDs try my first first (easiest) if no joy .... then go for it.
but this option should work ... virus or not - virus is software - delete re-load software .... virus gone (99.9999% of time) !!!
not sure what you mean here ...."keeps giving me a blue error screen and I have to choose between windows xp home or set up!!"
normally boot from CD .... then it's either repair or setup .. go setup ... delete partitions (note the size first!!!) ... recreate (same size) ...then install!
But If not .... Dell should provide Recovery CDs (they stopped for a while) so you may need to stamp your feet!!!
http://support.euro.dell.com/support/downloads /driverslist.aspx?c=uk&cs=ukdhs1&l=en&s=dhs&Se rviceTag=&SystemID=DIM_P4_9100&os=WW1&os