Hi, I Googled and found this page here Windows Update Fails 8000FFFF - TechNet Forums seems the user has similar problem, an answer is offered ( scroll down to find ) and is to do with un-installing a certain Hotfix. Hope this is usefull. In fact to save time I've cut and pasted the answer here..
Here is the answer to your problems. Go to your control panel under add and remove programs you will see a hot fix for kb929777. Uninstall this hot fix. Windows will tell you to reboot, do it. Download the kb929777 for the windows website not the auto update site, (if you do it will install the hot fix first before the kb929777 and then kb929777 will not install again). After successful update you will need to reboot. check for updates( there should be none and your history should show successful update on the kb929777. I also took out 3 gb of mem. before I did this but before it would still not download until I removed the hot fix, so I DO NOT KNOW IF YOU NEED TO REMOVE THE MEM. FIRST. But try it with the mem. in first and it may save you a step.