Constant 100% CPU Usage

Hi. I'm running Win XP Pro, on an Intel Celeron 700 MHZ laptop. (Probably mistake # 1 there lol). It's been installed for the past year or so with no problems, however just recently (within the past week), I've noticed that it's begun to run real slow at times. I go to Task Manager when this happens to find out what's causing it to slow down, and notice that "Explorer" is using 99% of the CPU. I'll then switch over to the "Performance Tab" and notice that "CPU Usage" is at a constant 100%. Rebooting resolves this, but it gets annoying to have to reboot whenever it happens. (once or twice a day). I'm behing a router/firewall, and my antivirus software is up to date, and I've scanned it several times, so I don't think there's a virus. Any help here would be appreciated. Thanks

 

XP likes to arbitrarily decide that certain (PCI) cards are "too old ". Check your system event log for these pesky notifications. One of my P-III systems uses a Maxtor (Promise) ATA100 PCI card. XP recently decided it was old and suddenly flicked up to random 100% cpu usage. it's fun.

*sigh*