I use an Olympus recorder and it records in the WMA format.
I could not get long WMA files to work in Express Scribe. They would just cut off, or the whole file wouldn't load. These files were three hours, four hours, and in one case over seven hours long. Converting the files to mp3 did not work either.
The next few depositions I recorded I started something new: I would start a new recording about every 90 minutes instead of making a long seven to eight hour recording. At the end of the day I had recorded a seven to eight hour deposition, but the files were broken up into segments of 90 minutes each so I had five separate recordings. My scopist reports to me that this worked in Express Scribe as WMA files. The files fully loaded and played all the way through without a hitch.