Most newer laptops come with built in wireless capabilities. To my knowledge it is still far from standard equipment in a desktop.
The Intel card do not support wireless, it is a standard Ethernet NIC. If the computer had wireless capabilities it would be on a separate card or usb device. It appears the only wireless option available from Dell for the dimension 1100 was an USB adapter. You would probably have noticed if you had one sticking out of an USB port.
Regarding buying a wireless adapter. I would suggest you buy one from Belkin. It is always a good idea to get one of the same brand as the router. It usually avoids incompatibility issues. Wireless USB devices should be pretty cheap (they are where I live at least) so I would get a new one. But I don't know the specific situation in Canada nor any good places to buy one.
But hang tight, hopefully someone else will.