Do you have some program called Webex Network Magic or similar installed?
many 0 byte files in vista temp folder "OPSD###.tmp" since network magic install?
http://forums.linksysbycisco.com/linksys/board/message?board.id=Network_Magic&thread.id=428
zero byte files created in C:\Users\Joe\AppData\Local\Temp\OPSD629.tmp after boot
See if isolating starting programs and non-Microsoft Services can isolate the cause.
310560 - How to Troubleshoot By Using the Msconfig Utility in Windows XP
http://support.microsoft.com/kb/310560
How to troubleshoot a problem by performing a clean boot in Windows Vista
http://support.microsoft.com/default.aspx/kb/929135
A program like Process Monitor might help you confirm what is creating these files.
Process Monitor v2.04
http://www.microsoft.com/technet/sysinternals/processesandthreads/processmonitor.mspx