well im able to play BF2 using a virtual mounted CD image
as for playing online with a keygen'd keys
it varies
most of the keys given by the keygen are already in use or globally banned.
some of them will still work and let you play a game. later on that key may be in use by some one else.
in the BF2/support folder you will find a key changer
after you have changed the key you will need to have the key encrypted in your registry to play on anything later then the 1.03 patch
to do this you can either reinstall the latest patch or use this program
http://www.mpcforum.com/showthread.php?t=113861