raidman.. wow, what a step up... this is what you need to do..
1) get more RAM... WinXP is a RAM hog, but runs smooth... If you cant afford it, it's best to hang out with XP until you can get some more. (MINIMUM requirements I tell my clients is 256MB for OK performance). Anything less makes you wish you had Win98 back!
2) NEVER upgrade a WINXP box. My reccomendation is to back everything up and get ready to move for a fresh install. Microsoft has TOO MANY known bugs for their upgrade process being that there are SOOOO many foundational differences between the XP platform and the Win9x/Me/DOS platform. MS knew of this, however went with the upgrade CD anyway (tisk tisk). Start off from scratch. And if you have the upgrade CD, I do believe MS will let you install fresh if you have a copy of an old OS around.
3) Enjoy.. this will take less time than trying to repair.
I know this isn't the best choice, but I NEVER EVER reccommend users to upgrade to XP without doing a fresh install to get there. The truth is, MS doesn't reccommend it either. :-/
Let me know if there is any problems!