Due to a number of questions and assumptions that arose due to what I suppose was my lack of explicitness, I shall try to clear the water here:
I didn't upgrade to XP from 2000 sooner because...
1) The default XP GUI sucks.
2) It's more of a resource hog than 2000.
3) You have to deal with activation and Windows Genuine Advantage.
4) XP wasn't really a good choice until SP2 came out, as SP2 combined with the earlier advances of SP1 to address many issues that XP suffered from.
5) I wasn't going to pay for a new version of Windows. My copy of XP (and Vista and 7 if I wish) was furnished by my university under Microsoft's MSDNAA program.
Other points...
-I never said XP itself was slow.
-I did say IE8 is slow on my configuration.
-Though the browsers themselves have responsibilities in this regard, our individual setups also determine program performance. A large number of factors play into this including OS, upgrade paths of the software which are installed, background processes, et cetera.
-I did an in-place upgrade from 2000 to XP to preserve my programs' installations and settings. Don't worry, I backed up everything before the XP upgrade happened.
-My computer is not old nor outdated, though like all of ours it could always use more upgrades. ;)
And on that note, I'll close by saying, "...Oh no, something on your computer is older now than it was a moment ago - better upgrade again!"