Vista - explorer.exe doesn't work anymore

Hello!
I am running Windows Vista Home Premium on a laptop HP Pavilion dv6000 and it was bought around february this year.
My computer automatically installed some updated without me noticing, and it restarted and everything (could the next windows version include an auto-save function for notepad, please? i lost everything i wrote, because i forgot to save...)... And when i logged in again, and everything kind of started properly... I realized that my wallpaper doesn't show up, no icons on the desktop, and the toolbar freezes and explorer.exe takes 50% cpu without doing anything at all.
now i can manage without the toolbar, but it is quite annoying anyway. the security updates i installed are (i'll just write the code numbers, because i am running windows in swedish)
KB956390
KB956841
KB957095
KB890830
KB954211
KB956391

and i have not installed service pack 1 yet. i didn't have enough space on my disk at first, but now i have deleted some files and there should be no problem to install the service pack 1, but when i click on "start installation", it just stops at "preparing installation".
edit: i got an error trying to install it. currently going to try the stand alone installation.

everything else runs just fine, and i don't see anything suspicious in the Task Manager, so it makes me think that it is not a virus.

does anyone have any ideas?

thanks for all comments.