Internal Hard drive being shown as DVD drive

Hello,
I recently salvaged a seagate baracuda 7200.7 160GB internal hard drive and I wanted to use it as an external hard drive. When connected, the drive shows up as a DVD-RW and wont let me in or reformat. Keeps asking for me to insert a disk. This is an internal hard drive by nature, if I can just wipe its memory and partitions clean, I know I can use it, but I've only ever needed to click on reformat to do so. I'm trying to find information online on how to wipe a hard drive clean without using a reformat function. Any ideas?