Today I unearthed an old hard drive with Windows XP on it. After a few hours twiddling I finally got the wireless to work on it... although even before that, the svchost application would make use of 99%+ of the processing time.

With just the default System Manager it's hard to find out what really takes time, so I downloaded procexp.exe from the Windows website (DON'T DOWNLOAD A VERSION FROM ANYWHERE ELSE!) and that showed me the tree and thus which tool was using all the processor time.

Surprise! Surprise!

The problem was the automatic windows update. (the update service is called wuauctl.exe in case you didn't know. It will also spawn a process called update.exe whenever it actually installs an update.)

The operating system runs a background process that uses 100% of the CPU... Quite interesting if you ask me.

Waiting for the updates to all be installed and after a few reboots the system will run normally (hopefully).