G'day Rick,
well, now there's a thing...
My previous comment was made from my PC at home and while I didn't specifically open an internet based file to test, I checked my history which I knew contained files I'd opened from the net (using Firefox) and they definitely were in the location pointed to by %temp% which is C:\DOCUME~1\lawrie\LOCALS~1\Temp\.
So, after reading your reply, I tested from my PC at my office (I love being the boss ) 'cos that's where I am, and from Firefox, they are stored in C:\WINDOWS\TEMP\ but from IE they are stored in:
C:\Documents and Settings\lawrie\Local Settings\Temporary Internet Files\Content.IE5\.....
My email client is Groupwise and those files end up in:
C:\DOCUME~1\lawrie\LOCALS~1\Temp\XPgrpwise\
This is the same as the machine at home.
I understand the email location which is consistent anyway, but I cannot understand why FF would put them in C:\WINDOWS\TEMP\ at my office and in %temp% at home. Both machines log into (almost) identically configured networks...