Indeed, most. But not some. If you want to be sure that it'll work, you need a crossover cable.
Take the cable you're using and move the plug boots back. If you're using a straight cable, it'll have a hardon both plugs connected symmetrically: 1 to 1, 2 to 2, etc. (look at the wire colours). I don't remember the exact configuration for a crossover cable, but it should be almost the same except for two pairs that are switched: i.e 2 to 6 and 3 to 5 or something like that.
However, if you say you can transfer data between computers, whatever config you're using works well. But I'm no network admin so I only know so much. In fact, I have two computers (XP and Vista) on LAN through a router and I can only "see" the other computer, but can't do anything else. If I need to tranfer a file, I either use a flash disk or fire up msn and transfer that way (f'd up isn't it)