wucrtupd.exe, the Windows Critical Update Notification program, insists on running every five minutes to check for critical updates. It may be well intentioned, but if the OS is so damn buggy that critical updates have to be searched for every five minutes, they should take it off the market. What’s worse, there’s no way I’ve found ’til now that to change the interval for good (running wucrtupd.exe resets the interval to 5 minutes). This page suggests something about sucrtupd.exe, which apparently exists for Windows98, but I run Windows 2000 and have an ‘updated version’ (according to windowsupdate.com) with such ‘advanced features’ helpfully removed.
Have disabled Critical Update Notification now (in HKLM..Windows..Run), and hope it stays that way.