What is your computer make & model?
Unless your computer is an older Macintosh, it is likely that your computer has IDE cables (Ultra ATA or PATA) and not SCSI.
Your new Seagate 80GB Serial ATA (SATA) hard drive can be used internally if you add a SATA HARD DISK CONTROLLER CARD into a free PCI slot. There are also SATA external enclosures that use USB2.0.
I have a 80gb seagate barracuda 7200.7 serial ata hard drive. It does not fit into my computer, (the cables are wrong) I think mine is scii instead of ata. I am wondering if I could buy something that would enable me turn this into a usb 2.0 external hard drive?