Boot / Reboot Hangs - Filling Up Status Bar Several Minutes

I have been suffering through a weird phenomenon lately. Whenever I go to IE the first time of any boot or reboot, it "hangs" after filling up the status bar for several minutes, then releases and all is well. (NOTE: I don't think this is IE-specific. It has happened booting apps, but I notice it most with IE as I use it extensively.) When things seem to lock up, EVERYTHING is locked up. I can't even bring up Task Manager, none of the icons in the Task Bar are active, etc. Sometimes I can Tab through other apps that are open, sometimes not, but when I can, the app is "frozen" until whatever is going on finishes. During this time, I can watch the process light (I have a Dell D600 laptop) going nuts. Before and after this event, I have run the system through the latest updates of utilities such as Ad-Aware Plus, Ad-Watch, PestPatrol, Symantec Antivirus, Ace Utilities, RegSeeker, etc., and none of them sends up a flag that anything is wrong.

My machine is always up-to-date via Windows Update feature, so I don't know what is causing this. I had the bright idea to reinstall XP SP2, but can't. Every time I try, it quits, giving me nothing more than a smal window with a red X in it and the notification that the install has been cancelled. I ordered the free XPSP2 CD just to see if that would make any difference, but I get the same error. I suspect I could attempt a slipstream install, but I don't want to go through all that if anyone out there recognizes this problem and knows what the solution is outside of doing a slipstream reinstall of SP2. Finally, I have several times done System Restores going back as far as I can, but while they have been successful (although I usually have to do the restore in Safe Mode as they will often fail otherwise), it has made no difference related to this problem.