reinstalled again

I have a sneaking suspicion that Windows Media Player might be (one of) the cause(s) of my problems. If I recall correctly, that was the last thing I installed yesterday before things broke today. And when I was reinstalling today, I got a weird message after I rebooted following upgrading Media Player to version 10 and installing the XP codecs. Or I guess it could be the Codec files, since they do change my windows registry...