When error message 80040203 shows up when running Windows Media Player 9, 10 Microsoft says they have no information on that error. This error may happen even while running other media players like ALC, Miro Democracy player, or DIVX and the video freezes, but unfortunately, those other media players don't always tell you an enumerator has gone invalid (whatever that means).
So how did I fix it?
1. Went to Add/Remove Programs
2. Removed/Uninstalled "Windows Essentials Media Codec Pack 1.0"
3. Tested an AVI file, all worked as normal.
Note: If you can not find "Windows Media Codec Pack 1.0," there is still hope.
I able to find one other instance of someone else who had this problem resolved without reinstalling Windows XP.1
Their solution was to go to download a different XP codec pack. I did not test that download myself, although the McAfee SiteAdvisor found no problem with the site when I checked it, but please see for yourself.
If for some reason it's still not working what I personally would do, is uninstall other media codecs too. It seems media codecs are the source of the problem. Please do any of this at your own risk, it's worked for me, it's worked for others, but computers sometimes seem to have a mind of their own. If your computer does have a mind of its own however, I think it would be happy to know you are trying to get its enumerator fixed.
Small jokes were included in this article to remind you to keep a sense of humor about things. "Oh yeah, I've only got like 30 videos I need to edit last week! lol!" That's what happened to me. I exaggerated a little bit, too. lol It took me a few weeks to figure out this problem. It was one not easily solved (well, not at all) by Google's help. However, now that I've written this article, it can be! I hope this solution has worked for you.