Vmware Tools Automatic Upgrade

We have been facing a problem in our environment to upgrade the vmware tools of our guests.
The problem is that some of the guests never automatically upgrades vmware tools even if you have enabled "Check and upgrade tools during power cycling" or selected "Upgrade Tools" within vmware tools tray.
Basically the guest does nothing after you trigger upgrade or power cycle.
After searching for a while we have found an article which has no relation with our case but somehow true and solved the problem.
The problem was caused by a prior vmware tools installation file "vmwaretoolsupgrader.exe" in C:\windows\temp directory to be deleted before triggering the upgrade. After deleting the file, everything works seamless. here is i link to the kb;

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1023459