Don't mean to disagree, but XP is extremely reliable. If you are having problems with it please provide a little more info about the specific problems you are having (and any relevant error messages you may be getting) and your HW setup.
I agree with allan I have been using windows XP for nearly a year (beta versions included) and found it extremely reliable - but unlike Windows98 it needs a little more understanding of the system - so you are able to fix any issues.
This is a great place to get help from - use it
You watch - I will get the BSOD in the next hour - however I have had this new puter since Feb 8th (no - I am not up 24/7 - only about 12 hours per day average) and have never seen a BSOD - my old Compaq (on Win98)was a regular crasher at about every 4 hours!
It sounds like your memory could be bad or something. I had a 128 MB piece that was incompatible with my system and it got recogonized as 256 MB so the OS would try to use the 128 MB that wasn't there and gave much the same error. That was with Windows ME though.