Premiere can't support a video format that it was literally just using

At work the video clips we upload to our computers are MXF files. We don't know how to format the cameras to not do that.

Anyway, the only way we've found to look at clips before renaming them is to drop them in premiere. Our computers don't have any media software and we don't have Administrative authority to buy or download one.

So I was going through clips in premiere today and relabeling them when I was done. But after I relabeled and tried putting them back in premiere suddenly the software didn't recognize the file format.

It had nothing to do with location of the files themselves. It won't use the file format it was just using when i went through the clips. What happened and how do I either fix premiere or reformat my files?