Fixing my Creative Zen Touch 20GB?

I recently bought this player from Argos at a heavily reduced price. More fool me then, because I had to go through endless hoops to get the thing to work with Windows Vista. However, I eventually succeeded in loading a raft of music onto it, but now realise that they are in lossless format and therefore wont play. As I attempted to, a 'Playback Error' message appeared, then the device froze! It wont even turn off! What, if anything, can be done to rectify this? And if I can get it to unfreeze, how do I go about loading the music I want in an acceptable (to the player at least) format that will play. There was no prompt or anything else that I could see to tell me that I had to convert the files when I was transferring them from my PC.