The other night I noticed the hard drive light on my laptop was solid for several minutes, indicating some fairly aggressive disk file IO. There were no open applications and I didn’t have any scheduled services running, not even the Windows 7 defrag (yeah, I still like to do everything manually). I also had a virtual Windows XP machine running inside Windows 7 but there were no open applications there, either. A knee-jerk reaction of mine when I see this is to open the Task Manager and look for any processes that are using an excessive amount of CPU time, but there were none, and the system remained mostly idle with respect to the CPU counter in both Windows 7 and the virtual machine it was hosting.
To see what was causing the unknown disk IO, I started by adding a few more columns to the Windows 7 Task manager: I/O Read, I/O Writes, I/O Read Bytes, and I/O Write Bytes. I sorted the columns by both read bytes and write bytes and the process using the most disk IO was the vpc.exe process, the Virtual PC:
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