Things to Know Before You Download Windows Vista SP1 ( this was part of an answer to a query I had sent to Microsoft. They are very helpful in providing information)
How to obtain the release notes for Windows Vista Service Pack 1
If you would like to install the SP1, please select KB935509, KB937287 and KB938371 to install and then do the following steps to install SP1.
Generally, of installation issues can occur if certain third party programs are running in the background during the upgrade (especially third party firewall, antivirus programs etc). As a result, Vista SP1 cannot be downloaded completely and the installation will fail. Therefore, I suggest we first perform the following steps to directly download Vista SP1 on our website in Normal Mode and then install it in Clean Boot mode to avoid software conflicts.
Before we try to install Vista SP1, please understand installing Vista SP1 requires a minimum of 5 GB free disk space on the Windows partition. The recommended free disk space is as follows:
• 7 GB Recommended for 32-bit Windows Vista
• 12 GB Recommended for 64-bit Windows Vista
Therefore, please make sure you have enough free disk space before installing Vista SP1.
If you are using a branded computer, which is also known as an OEM (Original Equipment Manufacturer) PC, the hardware and applications on your computer are highly customized by the original computer manufacturer. Therefore, the standard version of Vista SP1 may not be fully compatible with the computer system. At this point, I recommend contacting the computer manufacturer first before installing Vista SP1. Please ask them if any of the software applications and hardware drivers need to be updated for Vista SP1. Otherwise, installing Vista SP1 may cause unexpected problems. Thank you for your understanding.
They also sent a long guidance on how to install with the standalone installer. If there is interest in this, I will be glad to post it.