That generation of Gigabyte MoBo should support both SATA and IDE
One of My Rigs has a K8 Triton VIA K8M800
It has 2 - SATA and 2 - IDE connections, yours is probably similar.
SATA = Serial Advanced Technology Attachment
IDE = Integrated Drive electronics
SATA is faster and the interface cable/connector is smaller (good for saving space).
A 80GB Hard Disk Drive is the smallest recommended today, 250GB is getting to be the norm. Below is an example:
Shop around, you could probably get a better price.
BTW, which Linux OS are you installing?