First of all you make sure you use the latest version of FairUse4WM. At the moment it is v1.3 or 1.3 fix.

You may test Fairuse4wm on demo DRM protected files from fairuse4wm.com and ezdrm.com.

Note that some WM installations will have multiple ECC key-pairs, so you will likely have to "Extract Keys" using multiple licensed files. If you find a file that doesn't convert, try extracting keys wth it. Once your whole set of keys is extracted, you will no longer need to run WM per file.

To remove DRM protection from one-time play license files:

• Set your Windows Media player (WMP) to prompt on license acquisition
• Open the file, and let WMP acquire the license
• Do NOT click "Play", leave the WMP license window open
• While the window is open, you can use FairUse4WM on the file

If you experience problem using Fairuse4wm, but you have files you can re-download and re-acquire licenses for, you can re-individualize and try Fairuse4wm again. Back up your C:\Documents and Settings\All Users\DRM folder before re-individualizing, in case you need to restore it later.

After you re-individualize, try to unDRM your files first, before acquiring any new licenses. If it doesn't work, then try acquiring new licenses.
You can also try dropping the files into the list in Fairuse4wm, right-clicking and getting the key info, and then using that with drm2wmv, but it won't work for me (no private key found for the files).

You may find more help in the following thread
http://forum.doom9.org/showthread.php?t=114916