Macbook versus FS4104-AW wireless router

Hello,
I looked at the FAQ but didn't see the issue I have.
Our house runs a wireless network through an Aethra FS4104-AW wireless router connected to a Windows PC.
My MacBook used to work perfectly, for two years, without ever needing to jimmy around with any network settings at all.
But since then, three wireless Windows laptops have been added, and now my MacBook won't connect, or even detect, the wireless network outside of a two meter radius from the router.
I've since connected to several other wireless networks around town without any problems, so I don't believe the network card is broken.
Anyone got any suggestions on how to fix this issue?
I run OS X 10.4.11 on a first-generation MacBook.
I'll post more technical information if needed.

Buy and install a better router, one that will output a stronger signal. With all those machines feeding off an older router (vintage 2005 according to the manual) it's a wonder you're getting any signal at all.

Regards.