Sometimes, a failing hard drive can lead to this problem. My suspicion is that the PC keeps on looking for virtual memory on the problematic drive, doesn't find it on the flaky drive, and keeps on looking and looking. My other symptom was occasional problems opening files. The problem went away after I replaced the hard drive. Because of the drive's flakiness, it took me a long time to clone the drive, though, so it's always a good idea to make regular backups if you value your current Windows setup and or data.