Please help with external drive issue

I have a Maxtor DiamondMax 21 320gb PATA (ultra ATA) hard drive installed in an external case that I used on my previous OS - XP Professional. The case I had purchased from NewEgg and it worked really well via a USB connection. No software was necessary, I simply plugged it in a USB slot and it was displayed as a Mass Storage Device. I have tried the following with no luck:

1. Loading the latest MaxBlast software provided by Maxtor
2. Changing the jumper from Cable Select to Master and back

I am currently using Windows Vista Home Premium 64 with SP1 ...

Thank you most kindly in advance, Rob.