Do you have manual for it?
Just looked (Googled) some photos of it - the slot looks as if it's a PCMCIA Card slot but without checking the manual I wouldn't go shoving anything in there just yet.
---------- Post added at 18:24 ---------- Previous post was at 18:21 ----------
Ahh -
found it.
Is there a bulge next to the power socket? If so - that's the wireless....