Vista - Upgrade Installations Fail

Office 2007 (medialess oem) SP1 fails to install (all the other updates incl. kb946691 installed fine)
Adobe reader will not install
Autodesk Inventor 2009 SP1 wont install
The common theme seems to corrupt cab files. I've tried having the UAC turned off, it's a brand new machine without any antivirus on it (yet). I've tried to download and install all of these multiple times, I've even downloaded a few of them on a different computer to see if that was the problem.
Does anyone have any clues as to what could be causing these issues?

Try one of two things :

1) IN either the "run" window or "start search" off the Start Menu type in %temp% then press Enter. This will open the Temporary Files folder. Delete all the files present here. Some may fail to delete as an open process is using them. This is normal and fine. Reboot. Retry the update

2) Run "msconfig" in the same manor you ran the other command. Goto the startup tab and click "Disable All", click OK and reboot. Try the update. Once it completes, assuming it does, re-run that command, back to the startup tab and click "Enable All" and reboot.

Hi,
Thanks for the reply. Unfortunately the office sp still wouldn't install. It returns the message "this package failed to install".
I did get Adobe & Inventor sp to install before even trying this. In fact I didn't do anything differently than earlier when they wouldn't install.
this is getting frustrating.