You can use a simple .BAT file to clean out your Windows Temp folder every time you reboot your computer by opening Notepad and entering these lines into it:
rd %temp% /s /q
Save the file to your Desktop as 'cleantemp.bat'. Now click on the Start button and go to Programs then right-click on Startup. Select 'Open' to open the Startup folder then drag and drop the 'cleantemp.bat' file into this folder.
Now every time you reboot your computer, Windows will automatically delete all the files in your Temp folder. You should not, however, use this file to clean out your Temp folder at shutdown as this could cause problems with a newly installed program that requires you to reboot your computer.