I can't help you with your second problem, but I do know about the first.
In WMP goto Tools>Options>Filetypes (you might need to activate the menu bar first, that's another problem) and check the filetypes for which you want WMP to be the default player.
I have Windows XP with Windows Media Player and also Real Player, which is currently my default player. First, I would like to change the default back to windows media player but don't know how. Second, I would like to get prevouusly downloaded MP3s into My Library in Windows Media Player. I go to add to File> Add to my Library> Add Folder and then click OK. A search is always completed, but nothing is ever added to My Library. Kindly advise what I am doing wrong.