Officially out. If you are using an English, French, German,
Japanese or Spanish version of Vista, you should be able to receive
it via Windows Update (Start > All Programs Windows Update for
the new Start Menu or Start > Windows Update for the classic
Start Menu users).
Reference to read - http://support.microsoft.com/kb/948343
If you can't find it, kindly scroll down and read Cause 5 first.
If Cause 5 doesn't apply to you, scroll down and read Cause 6.
Cause 6 matters for those who installed Vista SP1 Release
Candidate or the beta. Or those who have automatic updates turned
on and got an earlier version of Vista SP1 on February. The
February version is the one that causes crashes on some computers.
If you are lucky and survive through it, Vista SP1 would have been
installed on your computer by now. Read through Cause 6 to remove
the patch and SP1.