Searching around didn't yield much, but I finally found a Japanese page that hinted at it being sleep mode. After doing a couple of tests with putting my machine in sleep and disabling drivers, it turned out that the Intel 82562 V ethernet adapter was the culprit. The Japanese page suggested setting ProcessorAffinityMask. That didn't work for me. Instead I just turned off all of the wake-on-lan abilities of the card:
- Go to Control Panels / Administrative Tools / Computer Management
- Click on device manager
- Select your network adapter under the "Network adapters" section in the right panel
- Select Properties
- Go to the Power Management Tab and uncheck all boxes. Here's a pic of the Power Management tab.
Hope that helps anyone who has this problem. At first I had written the CPU time being sucked up to Vista's amazing indexing service. But when I woke my computer this morning and the CPU was already above 47 C, I got a little suspicious. Turned out it was Intel's wake on lan feature. By the way, this was on an Inspiron 530, for those of you looking for the answer on Google.