wireless network, should be easy

i set up a wireless router and cable modem before and only hand to plug the cable modem in;
plug the router into that;
and then i was set up on a desktop and a laptop in the house;
signal was fine and everything was plugandplay;

however, at my parents house;
they have the same setup, but an ethernet cable was plugged from the router to the desktop (pc);
as long as this was plugged in, another pc laptop picked up the signal as well as my macbook;
if i unplugged the ethernet, neither comp picked up the wireless signal;
if i plugged the ethernet directly into my macbook it works fine;
shouldnt i just be able to have the ethernet unplugged and be able to pick up the wireless on both laptops?
someone else initially setup their network using wpa2 encryption;
where should i start looking to fix this?
router manufacturer/config?
isp?
the desktop that the ethernet is plugged into will turn on but the monitor (i dont think video card, but the actual monitor) is broken so i am hoping i dont have to go pick one up to fix this, because i travel by bicycle!

You are correct, there should be no problem running the wireless with either the ethernet-connected computer on the network or off it. I've done it many times.

What is the firewall setup? I'd set things up so the router is the only thing with a firewall running, not the individual computers. Whether you leave it that way depends on whether neighbors can get on your network or not.

If that doesn't help, go through the router settings for both wired and wireless connections. Double check that your laptops have the correct WPA settings, or shut off encryption as a test.

Good luck.

It sounds as though the desktop may be creating a wireless network and is sharing the internet connection over that. Just a possibility.

Regardless of that, connect the Macbook to the router with a cable and login to the router.

Ensure that the wireless function of the router is switched on and note the SSID (network name). Change the WPA password to ensure you know it's right, save the setting and disconnect the ethernet cable.

On your macbook click on the Airport icon on the menu bar and it should detect the wireless network (you'll see the SSID). Click to join, enter the new password and all should be well......fingers crossed.

thanks for the responses so far

when you say "whether you leave it this way depends on if your neighbors can get on your network or not"
i am not sure what you mean;
i thought if a firewall was on the router, and under the correct settings, it would prevent anyone else from getting on without some effort;
would having a firewall on the individual comps serve any purpose?
like, i am guessing it would make someone have to use cracking software twice;
once to access the network and again to access an individual comp;
i am not sure though as i have only been reading about this stuff and have yet to do any experimenting;
thanks to both responses;
mrplow (great handle btw) : i hadnt tried to access the router with the ethernet plugged into my macbook;
anything i should be wary of to make sure the windows laptop will still be able to access?

With a combination of Macs and PCs i think i would take mrplow idea and use the MacBook to go into the router and set up a new network name with at least WPA and then reconnect all units using the new password. On the MacBook you could turn the airport Off in the Menubar at night once u are done, which would be an effective block to malicious access.

problem solved thanks to mrplow, that name again is mrplow

for some closure on this problem:
i plugged into the router with the ethernet into my macbook;
went to the router settings (netgear) so it was something like router.net/basicsettings
it was actually set to wpa, so i changed to wpa2, changed ssid, network password, router password, made sure that wireless was enabled and applied changes;
now the macbook and windows laptop work fine without the old desktop being ethernetted in;
btw, at one point i wasnt sure of the old network pass so i just reset the router by holding in the reset with a paperclip for about 10 sec and while still holding in, unplugged the router, then plugged it back in (still holding down reset) and continued to hold reset once it was back on for about 20 sec;
then, with the ethernet plugged in, i was able to access router settings in browser by switching from the airport to ethernet (obv) on the macbook;
everything works well, but i am still curious as to what specifically created this issue;
i guess it had to do with the initial network setup through the desktop, but i am wondering, why?
even the people at the store where the router was purchased (i was told by my dad) said his laptop wouldnt connect without the desktop plugged in!
i knew this had to be inaccurate for so many reasons, such as if you bought a laptop, you would then have to buy a desktop if you wanted wireless access, lol

It definitely sounds like whoever configured the network had the desktop setup to share the internet connection rather than the router providing the wireless network.
The people at the store may have just been plain wrong but they may have had the impression that the desktop was connected directly via a cable modem rather than via a router.

Whichever.

Glad you got sorted.