Can't add mp3 files to iTunes playlist

[jamundj]

For some reason I'm no longer able to add mp3 files to an iTunes playlist. I can play the songs individually but can't make a playlist with the files. When I try to drag and drop them they just get a red cross and they don't get added.

Any suggestions on why this is and what to do?

 

[HBOC]

So the files are not in iTunes and you are trying to drag them into iTunes? Is this on a Windows or a Mac? Are the files DRM'd?

 

[jamundj]

So the files are not in iTunes and you are trying to drag them into iTunes? Is this on a Windows or a Mac? Are the files DRM'd?

The files are on my computer (PC) and i'm trying to drag and drop them into iTunes. If they're DMR'd I don't know (how do I check this?), but they are not purchased through iTunes. They are a mixture of CD rips and various downloads. The files are ripped from my iPhone to my PC using a program called SharePod. My old computer crashes, so I had to transfer them to my new computer. So now when I try to add them to a new playlist iTunes won't allow me to do so.
...Oh and iTunes won't allow me to play the songs directly from my iPhone either! They play fine on my iPhone, but through iTunes it's a no go!