1) Leave the SSD unplugged for now. Make sure the HDD is plugged in. After making sure you have all the data you want off the Vista Drive delete off all the partitions on the drive using the Win 7 setup to do so. When it comes to installing the OS it will ask you what drive to install it on. When you reach that point go into Drive Options (I believe it is called that) and there you will be able to delete the partition. Exit set up at that point.
2) Install Win 7 on to the SSD with the HDD disconnected. Once Win 7 is installed reattach the HDD and go to the start button, right click Computer. Click Manage, select Disk Manager and initialize the HDD. Partition and format the drive and it is now available for storage and your SSD is now the system drive.