path not found

Running xppro sp2 - recent clean reinstall.
Having problems with software updates - for example tried to install
..Net -downloaded via updates but faled to install.
So downloaded the full file frrom the ms site.
When I tried to install got a " path not found to C:\Documents and
Settings\#john\Local Settings\Temp\IXP000.TMP" message.
So I navigated to the Temp\IXP000.TMP folder clicked the exe and the install
ran OK.
The path not found seems to be a recurrent issue - same problem when
updating to Windows media player 10 - same solution ie manually navigating
to the folder.
Wondered if Zone Alarm Pro 6 could be causing the problem. However didn't
have these issues before reinstalling xppro -previously running all the same
software.
Any suggestions on how to resolve would be appreciated
TIA John