My politically-incorrect answer: if W2000 is working okay
and you have third party security utilities (most of them
are still necessary with XP), I recommend you stay with
what works as long as it works. W2000 is a stable
platform. There are mature drivers for it and is still
supported.
My computer is multi-user, so I had some incentive to
change. I had a special opportunity to get XP Pro
upgrades for all three computers in the house - two were
running 2000 and one was W98se - so I went for it. I am
not sorry, but frankly it wasn't worth the retail cost of
XP except possibly for mine.
If you do upgrade, I recommend a complete backup, format
and clean install. The XP upgrade over W2000 twists the
permissions quite a bit, and when I tried using the Files
and Settings Transfer Wizard to upgrade the hard drive
afterward, it all crumbled.
Mike