If it's a desktop, probably not.

If it's a laptop and bought within the last couple of years, probably yes. CHeck to see if there is a slot that looks sorta like a smaller version of a floppy drive (it'll be about two inches wide and have a button you can push to remove something) that's a wireless card port, so you'll have to buy one.

Otherwise, go to My Computer, right click and pick properties, go to the Hardware tab, choose Device Manager, and tell us what listed under 'Network Adapters'