For all those new users questioning about mp3 vs mpx vs wma for the
2201,2203,or 2204, I have found that unprotected wma is the easiest way to go
as long as you have the pmp folder (located in files section of this group) on your cf card.
I have never had a problem using cards ranging from the included 32 up to 256
MB and various usb and pcmcia card readers. I encode at 64 kbps ( I believe the upper limit is 96 kbps), but that is a
matter of personal preference. Forget about mp3/mpx and save
yourself a lot of time and trouble. MP3s will not play directly on these units
unless they are first converted to mpx using Real or other software.  
If you want to reencode existing mp3s to wma, or change wma encoding rate,
download a copy of dbpower Amp:

http://www.dbpoweramp.com/dmc.htm

Others have reported that dbPowerAMP 7 with WMA 8 at 64k/44Hz works best and 
you may have problems with more recent versions and codecs. You may also have to install the wmav8 codec.

All you have to do is download the pmp.zip from the files section of
this group, extract (unzip) it to your compact flash card ( you should end up with a pmp folder on the flash card with 5 files including wma.exe) via any reader and them copy wma files to the root(no sub folder) of the flash card. 

If you need the card reader drivers go to:
http://www.rca.com/content/viewdetail/1,,EI700643,00.html
or http://tinyurl.com/6wm8o