Windows Experience Index unavailable..

Hello,
My Vista Home Premium 32-bit PC recently stopped running the windows
experience assessment. It runs through all the tests then ends with a
dialogue box that says:
"Cannot complete assessment."
"The assessment or other operation did not complete successfully. This
is due to an error being reported from the operating system, driver, or
other component."

I have tried uninstalling and re-installing both my video and sound
drivers. I tried driver sweeper and driver cleaner pro. My videocard
and soundcard both work perfectly yet I cannot get the assessment to
complete. I also read many registry changes to no avail, as well as
multiple methods of emptying the DataStore directory in
Windows\Performance\WinSAT.

The WinSAT Log lists only the following error(s):
6445571 (5480) - winsat\main.cpp:1161: > Running Assessment: media
'-input {winsatencode.wmv} -encode {winsat.prx}'
6445961 (5480) - winsat\main.cpp:1430: > Assessment FAILED due to an error

If I run winsat formal -v, the log lists:
> Run Time 00:00:44.07
> Running: Media Decode/Encode Assessment v1.0.0.0 '-input
C:\Windows\Performance\WinSAT\winsatencode.wmv -encode
C:\Windows\Performance\WinSAT\\winsat.prx -v'
Initializing COM.
Creating temporary file for encoding output...
Temporary output file "C:\Users\owner\AppData\Local\Temp\wst51E8.tmp "
created.
Creating temporary file for ETW kernel trace...
Temporary trace file "C:\Users\owner\AppData\Local\Temp\wst51E9.tmp "
created.
Creating filter graph.
Loading encoder profile from "C:\Windows\Performance\WinSAT\\winsat.prx".
Creating encoder, saving to temporary file.
Disabling file sink.
Loading input file "C:\Windows\Performance\WinSAT\winsatencode.wm v".
FAIL: mediautils.cpp @ 592: 0x80040241 == VFW_E_CANNOT_LOAD_SOURCE_FILTER
(The source filter for this file could not be loaded.)
FAIL: mediatest.cpp @ 490: 0x80040241 == VFW_E_CANNOT_LOAD_SOURCE_FILTER
(The source filter for this file could not be loaded.)
Error: WinSAT failed to connect the input file to the WMV encoder.
Deleting temporary output file
"C:\Users\owner\AppData\Local\Temp\wst51E8.tmp ".
...
Deleting temporary ETW trace
"C:\Users\owner\AppData\Local\Temp\wst51E9.tmp "...

> Run Time 00:00:00.39
> MOOBE Run Time 00:00:46.11
> Running: Media Foundation Playback Assessment v1.0.0.0 '-input
C:\Windows\Performance\WinSAT\winsat.wmv -nopmp -v'
Creating temporary files for ETW tracing...
...
...

I can play both of the WMV files in the WinSAT directory so I do not
believe there is any problem with Media Player 11. I also tried
installing Windows Media Encoder 9 series (which lists it works with
Vista) and this also did not help.

Does anyone know what filters or media components are needed to fix the
above error? I have SP1 and also tried numerous restore points- none
fix the above problem.

Any hints or insights appreciated.