Can someone tell me what these files are

[OiO]

In a folder where I just save files for jewel cases, I found about 500 of these critters. They are all .idx files. I'd like to know what program could have placed them there, what are they used for and why there? I wanted to attach one so it can be examined but couldn't. Most of them are 32 bytes and 30 bytes. Thanks.

 

[crystal]

Check it out here