Just thought I'd describe my Vista 64-bit SP2 Installation experience so others will be ready for the long process. Have patience and it should install fine though.
Using Windows Update the download was relatively short; however, it took an eternity for the Microsoft server to begin the download. I went to bed hoping it would be ready to install the next morning, which it was.
From the time I clicked the post-download Install Button, it took 14:18 minutes to reach a window requesting restart. (I had disconnected my wi-Fi connection just before.)
Once I clicked restart, it went to through the post-install shutdown stages.
Stage 1 took 12:50 min.
Stage 2 took 16:47 min.
Stage 1 took 9:21 min. From the end of Stage 3 it took 2:53 min to return to the login screen.
After login it took 8:08 min for Vista to appear to be fully loaded. Some icons were missing from Notification Bar (I use the Task Manager Performance tab to determine when loading is complete).
The 2d restart took 2:19 min to reach login and 5:18 min more to fully load. All icons appeared properly in Notification Bar on the second restart.
NOTE. Soon after buying my Vista 64-bit laptop last year I had initiated an installation one day shortly before it began to rain. I shut it down during the install to complete it later. Something went arie and I had to reinstall the entire operating system. Do not Interrupt the installation process.