Slow connecction/short range

I have two notebooks on an Linksys 802.11g wireless network. Both use the
same type of wireless card and I've swapped the cards with no difference in
the results.

The older notebook [PII-450, 318MB RAM] , running Win98, has good signal
strength anywhere in the house and scores high on broadband speed tests. The
newer notebook [Athlon-M, 256MB RAM], running WinXP, has limited range and
scores much lower on the same speed test.

Any ideas where to look for a solution to get the newer unit to perform
better?

Thanks,

--
Erwin