Can't Install Win7 SP1

I've made repeated attempts to install Service Pack 1 (KB976932) and I.E. 9. Each time the download is successful and the update progress window says the update was successful, but when I reboot the configuration process stops unsuccessfully and Windows reverts to its pre-update state. Update History indicates all failed attempts.

I have applied the update repair utility offered by MS, I have run WindowsUpdateDig.cab, I've completely scanned my computer for malware (avast! and SuperAntiSpuware) and cleaned anything that was found. Some of the update attempts have actually left Windows unbootable and I've had to revert manually to an earlier restore point just to get back into the system.

The error code in the Windows Update History is 80073AA2. I've been through all the suggested fixes that come up from "Get help with this error." I don't know if there are other logs that would offer more detailed intications of what's going wrong.

A couple of other things of note - since my last attempt at SP1, I have been able to successfully apply a definition update for Windows Defender - KB915597. I have not, however, been able to get the update for User-Mode Driver Framework KB2685813 to install - it has failed several times in the same way the SP1 has. So this seems to be a selective problem.

Any help will be appreciated.

Karl

At this point I would backup all my important files and Wipe the drive then reinstall the OS. Then do the SP1 upgrade then reinstall my programs and copy the data back.

But that is just me. Maybe someone else will come along with a better idea.

But since you have been through all the so called fixes and it isn't fixed then the Reinstall is about the only option.

That's what I had been afraid was the next step. It isn't reinstalling the OS that puts me off, it's reinstalling all the programs I run, some of which need to be validated by their publishers. Fortunately, all of my data files are on a separate drive and backed up twice.

Oh, well, to work...

Thanks,
Karl

Oh, yeah, I left that out. I tried Windows Update Reset. Not only did it reset the update history, it wiped out all of my previous restore points. Fortunately, the one that was set by the next unsuccessful install attempt got me back to a bootable OS.

I guess, looking at the bright side, reinstalling Win7 will give me an excuse to buy a bigger drive for the new boot drive.

The OS and most of my program executables are on a 160 GB drive with 58 GB of free space. Could that be too little free space for the updates?