How much would UPS or a similar postal service charge to ship a gateway hard drive (computer tower)?

I don't know the weight of a computer hard drive. Therefore I cannot call and ask UPS. I visited a relative of mine for a while and while packing left my hard drive out. (My monitor made it back though.) I need to have my relative ship it and want to know the cost. Can someone please help? How much does it cost to ship a hard drive via U.S. Postal service, FedEx, Kinkos, etc. Please help soon!|||$5 at usps, $7 at ups/fedex