I received that error code 80080005 when trying to install Microsoft .NET
Framework 3.5 Service Pack 1 and .NET Framework 3.5 Family Update (KB951847)
x86 on my computer (Vista Home Premium, SP1).
I did a quick google search and came across the old 'turn off you anti virus
and firewall' tip. Since I had that issue with the SP1 update I tried that
and then I successfully updated my computer.
I learned a lesson that I had forgotten - when I see the phrase 'Service
Pack' I will remember to turn off my McAfee firewall and antivirus
Just passing this on. Dave Horne