Wow, it seems your Dell Inspiron 2600 is even older than my IBM ThinkPad T40 from 2003.
Your Dell does not come with an integrated wireless adapter (at least according to the reviews). Therefore, if it currently has a wireless card then it must have been installed into the PC card slot. The PC card slot is on the left side of the Dell Inspiron 2600 between the floppy drive and the network connector.
Apparently you do not have the manual, otherwise you could have easily found the answer. You can view and print the manual online at the following link:http://www.manualowl.com/m/Dell/Inspiron-2600/Manual/188175