An introduction to computer audio
WMP supports the WAV format.
It won't write tags in WAV (with one minor exception, see below)
Bit funny as this format is co-invented by Microsoft and IBM and technically you can write almost anything in RIFF chunks.
If you move the WAV's from your local HD to a another computer probably all meta information will be lost as it is stored in the library only.
More about WAV can be found here.
Only when ripping a CD to WAV a couple of RIFF Info Tags are written.
You can't change them afterwards.
The tags are:
ITRK (track number)
Thanks to ZachD