Yeah, 1st thing to check is that it is running on 802.11g and not b. 802.11g is the new 54mb protocol, and it the better of the 2. It does give a better signal range. I've got these:
Netgear DG834g Wireless Modem and Router

Netgear WG511v2 PCMCIA Card

Both use the 802.11g protocol, and I can get a very good signal throughout my whole house. And it's an old terrace with solid walls.
There are ways to upgrade the ariel on the router, have a look on google for "Pringle Can Ariel Upgrade"