Ok, this might be the weirdest PC performance issue I've ever seen. Starting sometime yesterday, my laptop starting running extremely slowly. Since it was nearly the end of the day, I just assumed some application (figured it was IE7) had just leaked some memory, and since I was shutting it off soon, didn't give it much thought.
However, this morning I was having the same issue. So I opened up Process Explorer to try and seeing what was eating all the CPU cycles. The only thing eating CPU was the Interrupts and DPCs. This really had me scratching my head. What the heck would be causing my PC to slow down so much?
A quick search on 'Net lead me to a forum post that indicated USB issues could cause DPC CPU spikes. So, I look over at my laptop and notice I still have a USB cable plugged in to my laptop, that is not plugged into anything.
I had used the cable yesterday to charge my cell phone, and just unplugged the cell phone w/out unplugging the USB from the laptop. So, I yanked the USB cable out just to see what happens.
Sure enough, within seconds of unplugging the USB cable, the CPU spikes stop and the system returns to its normal state. I'm not sure if the problem stemmed from Microsoft's ActiveSync application or whether it was just the fact that Windows XP SP2 kept polling the USB port for a device since it found a plugged in cable, but either way I've got to remember not to leave in a USB cable that's not attached to anything. Talk about weird!