Most cd drives have logos for the functions and speeds it supports.
For instance, on the fron of mine it clearly reads "DVD R/RW" (DVD read/write), "RW" (not quite sure what this means), and "Compact Disc rewritable" (meaning it can readwrite CD's).
If you have a store bought PC (which is highly unrecomended for gaming [unless its from a company that specifically produces gaming machines]) or a cd drive face plate, just open the door with a tool. Also, if all else fails, you can remove the drive, there should be a label attached to the side that describes all that it supports.