Microsoft pushed four updates to Windows Vista x64 systems yesterday, and one of them is causing problems for some people.

Microsoft KB Article 973879 was released on August 25, 2009. It is supposed to resolve a problem on Windows Vista x64 (based on Intel 64-bit CPUs) in which a BSOD happens when installing Windows Vista SP2.

However, on Hewlett-Packard Pavilion DV7 notebooks, installing this update, which is supposed to prevent Windows Vista from crashing, is rumored to actually cause Windows Vista to crash.

(The article author initially didn't know precisely which update was causing the crash.)

My office has confirmed that this update does indeed crash Windows Vista on an HP Pavilion DV7, although the type of failure was a snow crash. The computer froze and became completely unresponsive at the instant of the crash: the arrow did not move or animate, and all the off-screen indicator lights froze in the state they had (on or off) at the instant of the crash, including the hard drive activity light.

There are two workarounds, both of which are essentially to rip the update out of Windows Vista. Start the computer in Safe Mode by mashing the F8 key just as the HP logo vanishes, then using the arrow and enter keys to choose "Safe Mode."

If you have a restore point for it, choose Start -> All Programs -> Accessories -> System Tools -> System Restore, and choose the Windows Update event that installed the update.

Otherwise, instead of using System Restore, choose Start -> Control Panel -> Programs and Features -> KB937879 -> Remove.  You may have to hit the "Show Installed Updates" link in the left column to make KB937879 visible.

Reboot your computer, then do not let Windows Update install the update again.