Suddenly every time I attempt to play an online video using media player, I get the "Media Player cannot play the file because of a network error...." message. I played with the proxy settings in Media Player, updated the media player to no avail.

I also like to play the XP online backgammon game. Now I can't connect to their server. My other systems have no problem. This started at the same time as the player issue.

I've run chkdsk /r in Recovery Console and it didn't work. I don't want to run an over-the-top install if I don't have to. This one has me stumped. Any other ideas?

The TCP/IP stack could be corrupted; take a look here:
http://support.microsoft.com/kb/299357

Hmm...that didn't do it. That's the same as the Winsock repair tool, isn't is? It resets the TCP stack, too. Anyway, I followed the instructions on the MS page and it didn't work. This only affects media player and the games. Nothing else is botheres. If I download a media player file to the system, it will work. If I click on the same online, it won't. Hmmmmm.....

I’m not sure that the Winsock repair tool can reset the TCP/IP stack, but you can give it a try:
http://www.snapfiles.com/get/winsockxpfix.html
You can also try a System Restore, or the Netsh.exe Tool:
http://support.microsoft.com/kb/242468

Well, I've tried everything, including an over-the-top repair install....and nothing. Now some of my programs can't update. Looks like I'm going to backup, wipe and reformat. Bah! I hate doing that.

Something got messed up big time with your system I guess; sorry about that John, but you know what they say, “it happens.”