Windows 7 Transferring Data From Old To New

I have an externally connected (by way of USB) samsung hard drive from my dead HP Slimline Vista connected to my newer HP Slimline Windows 7. The old drive powers and runs and the new computer recognizes it in printers and devices but I can't open it to access files etc. I know the old drive was formatted with Vista and 7 can't read the old drive. But it's my understanding that there are drivers that should be able to open and allow me to read and transfer from the old to the new. I can't install the old hard drive in the new computer because there are no extra connections or slots to mount it.

Thanks Everyone,

Steve