Wireless Network Problem

Hello,

I was wondering if someone could help me with my network problem.

Ok, I have 25 computers in my apartment. I have 22 of them on ethernet cords in one room and 3 desktops (#9, #10, #21) around the apartment on wireless. I have a business that I run and #9 holds all the business files on its shared network. I just set the wireless network up and #9 and 10 both access the internet fine. #10 can access the files on #9's shared doc's fine. The problem is #21 is having trouble accessing the internert and shared files. It works but is very slow. I have a linksys router and all 3 are linksys USB recievers. They are all about the same distance from the router. #9 and 10 are both the same compaq desktop while #21 is a sony desktop. I can't understand why 21 is struggling to recieve internet and files. Can anyone provide a suggestion?
Thanks
Brian

 

also im on a B network...wondering if G or higher would help?

 

what's the signal like on #21. Just because it's the same distance doesn't mean you get the same signal, differences in wall construction may block the signal, electrical panels tend to do the same thing.