Win7x64 - trouble installing SP1

A client brought me a tower PC (HP) due to a file association problem; I fixed that w/o problems. Online updates weren't working, but I fixed that. A MalwareBytes scan removed over 500 items, almost all were related to toolbars, browser helpers, and other such ad-based nonsense. The main problem is that Service Pack 1 for Win7x64 will not install. I've tried using Windows Update twice, failed. Using a different PC, I downloaded the SP and burned it to disc, didn't successfully install. I used yet another PC for the download and put it on a flash drive, that didn't work. The install looks like everything is OK until the very end and then I get a "not successful - element not found" message, when I click the "Details" link, it says "ERROR_NOT_FOUND (0X80070490)". This is usually after a reboot. A bit of research said it was a problem w/ the Windows Service Store, or possibly the antivirus software was blocking it, so I uninstalled Avast; still could not successfully install SP1. I used the Microsoft Troubleshooter (useless), I used the Update Readiness Tool which installed a Hotfix, that failed. The good ol' SFC didn't fix it. I tried everything suggested at this link, and none of it helped.

Everything else works fine, the PC is fast, other online updates for Windows (and everything else) work, it's only SP1 that won't install.

HELP!!!!

Thanks

 

Thx for the response plodr. I'm going to check out the links you provided above in a minute or two. A clean OS reload is out of the question because the client does not have his install discs for Office and Works and Quicken; an in-place upgrade might work, but I don't have a Win7 disc w/o SP1. Can I use a Win7 install disc with SP1 included to do the in-place upgrade on a Win7 system w/o the service pack?

Thanks again!

(the video is on-board... it's ATI Radeon HD4200)

 

I'm downloading the ATI driver now as it seems to be the easiest thing to start with today. I've tried just about everything in the 2nd link provided above; I tried all that stuff a couple of days ago, including sfc /scannow, and I used an ERD PE boot disc which also has sfc built in to it; neither of them ran correctly and did not fix the problem. I also tried the Tweaking.com Windows Repair Tool and that didn't fix the issue either.

 

Removing the old video driver and installing the newest available did not allow for successful install of SP1 either

 

I read online somewhere that storage drivers can cause the problem I'm having so I updated the SATA drivers and disconnected the SD/MMC reader from the motherboard (the reader is built in to the tower). This didn't work either. The HP site has no drivers for the SD/MMC reader and device manager lists them as "generic". Maybe I'll try uninstalling the drivers before unplugging the reader, then try the SP1 install again. It just takes so freekin' long to see if it's going to fail or not...

The PC model is Pavilion P6654Y if it matters, with Win7 X64 Home Premium, obviously no service pack

 

I gave up. The client needed the PC, everything else was working fine so I explained that if he backed up all of his data (140gb or more of work files, payroll files, etc) and provided install discs for QuickBooks, Works, Office and brought it back to me, I'd perform a full complete clean re-install of Windows7 with the service pack. I had already spent a combined 16-18 hours trying to fix it. Since a service pack install can take over an hour, plus the time implementing fixes, it was getting ridiculous. The only way to know if the SP took was to install it and see if it failed, and it would only fail right at the very end.

:mad