updates failing in WU, and SP1-issue

Hey

I'm having problems getting updates via Windows Update (WU) on Vista Buisness 64bit edition
When trying to install SP1(KB936330) for Vista 64bit i get the 80070057-error, but i've also gotten the error

before. After a fresh install (no additional programs installed) of Vista Buisness 64bit I run WU.
It finds a load of available updates, and after trying to install all the "important"-ones, i usually get the report

saying that, normally, half of them were succesfully installed, and the rest failed.

I repeat the procedure until I've only got 1 update left, wich is usually "Cumulative Security Update for Windows

64bit edition" (KB947864). After approx. 3 tries, I try to manually install the update, wich doesn't work either

(The error is "The update does not apply to your system"). So, if I'm lucky, i get a successful update after roughly

12 tries. This only results in me getting the ecactly same errors with SP1(KB936330). But this wont just "luckily"

install after trying numerous times. I'm totally stuck.

Here is a list of the things I've already tried:
Reinstall a fresh Vista 64
Reinstall a fresh Vista 64 with another CD
The upgrade function from the Vista-CD
Downloading and installing SP1 manually (stops midway in the installation and closes the installer and gives no

feedback)
Downloading and installing other updates manually (error when executing the files, saying "The update does not apply

to your system")
Reinstall a fresh Vista 64 and then trying to install SP1 manually (get an error saying: ?????????????)

It's also worth mentioning that during all my tries, apart from the first one, I haven't installed any other program

before running WU.

My computer have the follwing specs:
Tower: Antec Performance One P182
Mainboard: MSI P35 Platinum
CPU: Intel Core 2 Duo E8400 3.0GHz Bulk (LGA775)
CPU-cooler: Scythe Scythe Ninja PLUS Rev. B, without fan
Harddrive: Samsung SpinPoint T166 500GB SATA2 16MB 7200RPM
Harddrive: Seagate Barracuda 7200.7 160GB S-ATA 8MB cache 7200RPM NCQ
Graphics: Point of View GeForce 8800GTS 320MB DDR3
DVD: Samsung DVD Recorder 20x +R/+RW -R -RW Lightscribe SATA Black (SH-S203P/BEBN)
Temp: 34 C when idle, and max 45 C when busy

I'm beginning to think the issue is hardware-related, because a friend of mine installed Vista 64 just fine, without

errors when running WU at all...

Can anyone help me please?