So I have been using Guitar Pro (a midi-based guitar tablature program), but now it, and audacity, refuse to access the midi library correctly. If I play a midi song on Windows Media Player and while it's playing play a guitar pro song, the guitar pro song will actually play. Anyone know how to fix this?

Also: Audacity (unlike guitar pro) gives me an error message:

Oh c'mon SOMEBODY has to wanna help. I can't believe I only have 9 views...

I viewed it but i can't help =( I have guitar pro but I only download the tabs to practice songs with.

Your midi driver might be corrupted? You might have to reinstall i dunno

Thanks for at least putting that little bit down, at least the despair has faded a tiny bit.

I wasn't sure what was happening (not very detailed description) and was far from having an educated guess why, so I waited if someone else has something before jumping in with my nonsense.

Wait, what you're saying is that you are using your guitar pro the same time you use Windows Media player and WMP just doesn't play (as does Audacity but with an error message)?

Sounds like guitar pro is somehow blocking your sound card. I know that from former times when I record something I can't start another recording. Maybe it's something related. There might even be an exclusive / multi mode setting on your sound card or in guitar pro.
You could always try reinstalling both sound drivers and guitar pro since - if I understood you right - it has worked at some point in the past. Don't forget to completely remove them first. We don't want to have any settings file or reg entry be left over.