Ipod won't work in new Car stereo USB port

I purchased a new 1GB Ipod and a Jensen new car stereo with built-in USB compatable port. I linked the IP into the PC at the dealership and loaded a few songs from there PC to see if the device would work in the car usb port. It worked good. I took the IPOD home relinked it to my new Dell 4700 loaded the songs with auto-fill and can listen with headsets, but not on the car USB port. I keep getting checking,checking...no files found. I tested a seperate 512 Gb IPod on a seperate PC that has Itunes loaded and plugged it into my car usb and it worked good. Problem: I can do everything on my 1GB IPOD except make it work in my car stereo. Is there some service I don't have on or setting I need to make on my Dell box to download the proper files to my IP so it will work in my car usb port.

Thanks Spiceman