Windows XP not booting up properly
I'm currently posting from my own laptop, but my family's main computer isn't doing so well. Everything was working fine last night, no problems with shut down or anything else for that matter, but this morning when my dad turned on the computer, Windows refused to finish loading. We are running XP SP1 (I hate SP2 -- it basically killed wireless networking on another family laptop and did more damage than good). If I start up the computer, it seems like everything is running as usual, but once the desktop starts to load, then things go funky. Only about a third of the icons on the desktop load completely, and if I move my cursor over the taskbar, I get the infamous hourglass. Taskbar icons don't load at all -- the clock loads but not the usual Norton icons, etc.; no Quick Launch, and the start menu is unclickable. Nothing on the desktop is clickable, either. The only thing that I've been able to do is run Task Manager, and thank goodness since that seems to be the only way to shut down/restart properly. I've also tried running the computer in Safe Mode, but I get the same results. Whenever I try to shut down or restart, I get an "End Program - explorer.exe" pop-up, so obviously obviously something's up with Windows Explorer.
Anyway, I'd appreciate any help that I can get, and if you need more details just ask.