Windows Media Player 12 Encountered a Problem

I'm running Windows 7 on an offline PC that I use for photo editing. I usually listen to music running on my other online PC while I'm editing but occasionally listen to music on the offline machine, but when I came to try this morning WMP 12 gave me the "...has encountered a problem while playing the file".

As it's an offline machine I can't use the Web Help option, but have been through the troubleshooting process and re-booted several times. The only install I can think of has been a trial version of Photoshop CS5 but I've un-installed that now and tried again and still the same problem. I also tried the "regsvr32 wmp.dll" command but received another error which I assumed was due to the machine being offline.

Anyone have any ideas what could have caused it to work one week and then stop working the next?

Thanks in advance.
Chris

Hi, do you have little speaker tray icon near clock ?