A friend of mine, Chris Fenly from Waterstons, got in touch today about a weird problem he was having with two Windows XP SP 2 machines running Office 2003.  Opening Word or Outlook generated the error "Outlook could not create the work file. Check the temp environment variable."  It's an issue which a few people seem to have according to Internet search engines.  Anyway, before I could be of any help, he'd fixed it. 

On his machines HKCU\Software\Microsoft\Windows\Current Version\Explorer\User Shell Folders\Cache was pointing to %windir%\temp.  He changed it to C:\Windows\temp and all was well.  I didn't ask where his %windir% variable was pointing at the time - I wish I had now.