Little update for my codec installs (maybe a little off topic)
With windows 7 pro x64 I now have all but rmvb (no sound and not exactly a huge loss

) working in both x64 and x32 wmp and x64 media center. No reg hacks or anything required and it's all appears to be using the built in media foundation codecs where possible
In case others are interested installed k-lite x64 pack, ensuring that ffdshow (audio and video) and matroska splitters are to be installed. Everything is unticked in ffdshow except for rmvb, theora and vorbis codecs (not built in

).
Then installed CCCP 32bit codecs - removed ticks on everything but theora and vorbis at install and then checked in ffdshow that only rmvb, theora and vorbis were ticked.
Subs are dealt with via directvobsub (or more precisely vsfilter) plus the latest matroska splitter (in cccp) for dealing with auto selection of multiple audio/subs tracks.
So thinking about it after the above - all I actually need when I install the new gpu I'm after and reinstall the os is directvobsub (vsfilter), ffdshow and matroska plus the above configs and I'll have everything working nice and clean