I'm getting a failure when trying to install SP2 over Quartus 9.0.
My machine is running Vista Home 64 bit.
Quartus 9.0 is already insatlled and works fine.
I downloaded SP2 and saved it to the desktop.
When I run the .EXE to install, the installer wizard begins, but after a minute I get a popup window that states that Quartus 9.0 "...is not installed on this machine. The patch setup will exit now."
There seems to be no way around this.