I used Windows Media Player and it worked great. You can use .wma or .mp3 formats. You CANNOT use a 6GB card. I know you can use up to 2GB, but I did not try it beyond that. Anything over 4GB is definitely out of the question. Different technology used over 4GB. I used mainly 1GB cards and get over 200 songs on a card recording at the best quality. I found a small, hard case that holds 8 SD cards that I carry with me, available at Best Buy. I can't remember how much it was, but definitely under $10. If you need to have quick access to more than 1600+ songs with you at all times, you are out of my league. I know I've ridden over 450 miles in a day and wasn't finished listening to a 1GB card. Get the 2 GB cards are you have over 3200 songs in the player or in your bags and probably a 1000 mile trip without changing the card. If you need help using Windows Media Player to record onto the cards, I can probably walk you through it. I just traded my bike with the MP3 player last week, so now I'm wondering if there is a way to record a lot of mp3's onto a CD, or do I need to get the HA-90 again? It's a great unit, but I think everyone that gets one has lots of questions initially that the manual does not address. When I got mine, I contacted the company that makes it for Harley and let me tell you, they really didn't want to give me answers to anything.