ad hoc or infrastructure mode for best connectivity

I have a simple home wireless network. I have dsl internet that runs
from my cable modem to my linksys wifi router that is wired to my
desktop. I have one laptop that I connect directly. It's 802.11g and
the laptop disconnects 'frequently' - anywhere from once per day to
once per week. It seems to be random, e.g. it will be connected when
one person is logged on in WinXP but when you log out and log in as
somebody else, you can't connect. Sometimes you can 'repair' the
connection but not always. You can always connect after unplugging
and replugging the router, even if only for a split second. It's all
extremely frustrating. It's in ad hoc mode but I thought maybe
infrastructure mode would solve my problem but I don't wonat to go
through that trouble for nothing. Any tips?