Most computers yes (actually all non broken computers), most cars, no. If you want a car CD player that plays MP3 files, you pretty much have to buy one. Honda may offer that option these days, but it seems to me that since the work has pretty much opted to store their digital music on iPods, it’s far more likely that if they wanted to upgrade the stereo on base model car, they would if anything include a line in jack for your digital media player. I actually had a car CD player that played MP3 files for a while, bought it I think in 2001 or somewhere around there, back then we had MP3s, but digital players to use them on hadn’t really become a household item. Within 2 or 3 years, that changed, but the popularity of MP3s encoded onto CD never really took off. I remember that I could put about 11 CDs worth of material on one disc, and it was great to listen to that in my car, took up a LOT less space, but these days even your smallest clip on devices store more music than one CD, so it’s become pointless. I would say, look at the stereo in the car, if it doesn’t say “MP3” somewhere on the face, it doesn’t play MP3 discs.