Wireless and wired problem

I have a wireless network running just fine except for one problem of
dropping the network connection randomly. Are there any timeout parameters
that shut down the connection with no activity for some timeperiod?

My really big problems is I added a wired network for a network printer. Two
computers and a printer are connected together on a switch. I have to disable
the wired network connection on a computer to access the network through the
wireless router. There is no internet on the wired network. I then have to
enabled the network again to print from that computer. Why is the wired
network assumed to have an internet connection? I'm using XP Proffesional.

Thanks in advance

John