You may safely rename .WMV to .ASF and vice versa and play them in any player supporting Windows Media videos. The only difference I have noticed was that .ASF files can be un-indexed so that you're not allowed to fast forward or rewind, but WM Recorder can automatically index .ASF files while recording.

As for .dat files in the cache folder, they're useless. Haven't seen any program that can make them playable.