Spyware (software that you don't realize you have because it piggybacked on something else you downloaded,
like Kazaa) can gum up the works of an SP2 installation.
Scan your hard drive using a free program like:
Spybot Search & Destroy (safer-networking.org)
spywareinfo.com/ (not found 2004/10/31)
spywareinfo.com/downloads.php (not found 2004/10/31)
to make sure your PC is free of these programs.
For more instructions, see: shack news.