Vista - [SOLUTION] shaderapidx9.dll related crashes on Vista

I've seen plenty of posts around here asking for help with games crashing on
Windows Vista and shaderapidx9.dll being cited as the cause. I had the same
problems myself, and none of the fixes i found worked (Steam's FAQ page, the
resolution tricks, etc).

So I went around and googled. The problem has to do with a WMI problem in
Vista. It seems to be caused after installing certain versions of AIM and
other IM programs from what I've seen. This happened to me after I installed
the newest "classic" version of AIM.

It seems that valve knows the problem has to do with WMI, but looking at
their support page for it, they dont have the solution.

Anyway, I came up with this after looking on MS forums.

BEFORE you do this, make sure this is actually the problem. One easy way to
tell is by trying to access the "Network and Sharing Center" or by looking at
the network icon in your taskbar. If you cant get into the network center or
if the network icon has a red X and youre sure you are connected to
something, then you have a WMI problem.

Another way to check is by going into Control Panel > Administrative Tools >
Computer Management > Services and Applications (on the left menu) > WMI
Control > More Actions (on the right) > Properties.
If theres a WMI issue, you'll see some sort of error saying access denied.

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For users with Windows Vista Ultimate or Business editions:
(Credit goes to blueshot from MS forums)
----------------------------------------------------------
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For users with the Home editions of Vista:
(Credit goes to SWAndersen)
Go to the command prompt (hit run and type in cmd.exe)
and type this in:

net localgroup Administrators /add Local Service

(optional)
then you can type this in:

net localgroup Administrators

and if LOCAL NT AUTHORITY/SERVICE is listed, then it worked. Now go reboot.