Vista Pre-SP1 Update Mystery Solved

In late February, Microsoft pulled update KB937287 after it sent some computers into endless reboot cycles. Microsoft refers to KB937287 as SSU, or Servicing Stack Update.

An unidentified post on the Windows Update Team blog explains what went wrong:

"The SSU has special code to check whether there are any pending reboots or other updates to install. If it sees either of these circumstances, it prevents the install from starting. During our investigation, we discovered that there were a few unknown and rare events during the middle of the installation of the update that could cause the update to think it needed a reboot to complete the installation. If this happened, the system entered a repeating reboot loop."

Because of my earlier reading support forum traffic about the update, "a few unknown and rare events" elicited a chuckle.

If I rightly read the blog, Microsoft will release a pre-prerequisite update to fix the problem:

"To address this problem for people who have not already installed the SSU, we are releasing a fix tomorrow which will install prior to the SP1 Servicing Stack Update. This pre-SSU update helps to ensure a smooth install of the SSU by working to prevent the system from rebooting during the SP1 SSU installation. We also made additional changes to the SSU installer code, so that it checks for and requires the pre-SSU (KB949939) before it will install."

Pre-Pre-SP1 Update? You've got to love Microsoft.

KB937287 hosed my wife's Vista PC. I'll install the updates tomorrow and report back.