The following solution from http://forums.cnet.com/7726-6644_102-2532473.html?tag=posts;msg2532473:
Windows Media Player 11 won’t open – Solution!
I had the same problem and I believe I have solved the problem. Follow the instructions below:
1. Click Start, click Accessories, the right click on Command Prompt and choose “run as administrator”, then type regsvr32 jscript.dll, and then hit enter.
2. Type regsvr32 vbscript.dll then hit enter.
3. Now type exit and hit enter. Now try media player and it should work.