I was getting the same errors on XP but this little download took care of that you guys should google it to find the link it's called ffdshow hope this helps. I also found an add on to wme that allows for multiple avi files at one time which could help with encoding tv shows. If the link does not work for it just copy and paste it nice tutorial though. Get his profile and the SDK for WME from the site and ffdshow is just codecs for it.
http://zunetips.wordpress.com/video-conversion/