If your board supports SATA, get that. It's newer and faster. You could leave the OS on your 30gb and put your new drive in as a slave and move stuff like your My Documents onto your new drive, keeping just your OS stuff on your old drive. I would think you'd want to partition your new drive for your OS and everything anyway, and unless your 30gb is really slow or something, it'd be a fine size for just the OS stuff. I did that to my grandfather's computer. He had a 30gb and bought an 80gb, and I just left the 30 in for the OS and moved his My Documents and other files to his new 80gb.