mmk, I have three computers in my room, 1 laptop, 2 desktops... the laptop used to have vista, but I downgraded to XP ^_^ and it works great with the wireless network we have at home, internet's fine and all..
 
the main desktop is where i'm having a problem, it had XP on it originally, has had a linksys G network card in it I think since I bought it, used to work O.K. when I had it downstairs.. I moved it upstairs and I can no longer get a good connection, and when it does get connection, its not very good and doesn't recognize the internet
 
The router we have is the basic one (I guess) that comes with the new Verizon Fios package or whatever...
 
I also have the old linksys G router we used to use with our old IP I was thinking of making into a gateway router for the Fios one..
 
I was thinking of upgrading the main desktop anyways, but an option that made the main desktop work so that I can upgrade that, and put all that into the secondary desktop and upgrade the main desktop would be great, but not necessary

Generic wireless routers and walls/ceilings don't get along that well.  Your house may be a little on the dense side which could cause the problem.  Have you tried boosting the signal power on your router?
 
You could try putting the linksys router as close as possible to the computer, whether you have it upstairs or downstairs and then wiring it into your FiOS router...chances are that two basic routers are not going to be capable of working together as a string of APs without being physically connected.  Just make sure they operate on different frequencies/SSIDs.
 
Alternatively, Cat5/6 cable is designed to work at full speed for 100m, you could just run cable through the walls, buy in bulk and it'd be cheap!