Shared ADSL fine but network blind?

Sorry if this is asking the obvious but I'm a networking
newbie I'm afraid.

I've just got a 2Mb ADSL connection and have set up a
Kcorp KLG-575 (108+G) wireless router and a D-Link 300T
modem serving:

XP (HE) SP2 desktop - ethernet connection to the router
XP (HE) SP2 laptop - wireless 108+ connection

1/. Both computers access the ADSL connection just fine
but how on earth do I get them to be able to see each
other so I can access each other's files? I set up the
router on its web based interface and am currently running
it on 64 bit WEP.

2/. I've set MAC filtering for just these 2 machines
alone. Will this stop another outsider logging on
wirelessly to the router?

Many thanks.

Steve