Ipod 30gb. My Packard Bell Computer runs Windows Vista. When I first connected the ipod to the

Question

My Packard Bell Computer runs Windows Vista. When I first connected the ipod to the computer it showed up under 'Computer' drive K: and installed iTunes and downloaded some songs and that was fine put it in my i-station speaker dock then put it back onto the computer and the computer had taken it off of 'Computer'. When I downloaded driver detective the scan showed the ipod as being on a System Driver?? Have been trying for 4 days now to work this out? Basically my computer
does not read it as a portable device. Have tried the reset but stays in 'disk mode' does not go into 'please do not disconnect'. Have plugged it into the usb at the back of the hard drive instead of the front (incase it needs more power as some suggest). Have un-installed/re-installed iTunes etc. Have turned the power off at the wall and also restored it to an early time before I had the ipod. It's so frustrating I just need someone to tell me who has got the knowledge about these things.
Please help.
Sally