Office network configuration?

The use of a switch is really not necessary. If you have a Modem Router combined, any wireless computers shouldn't be a problem to connect. Depending on the amount of ethernet ports on the Modem/Router will determine the amount you can connect by hard wire method.

If you are using a 2nd router it must be confiqured not to distribute IP's, this enables the Modem Router to distribute the IP's

It's impossible to give a correct answer given the information above. The main problem is using wireless, cable is best. You could run some diagnostic software and it may give you some clues ..

www.wireshark.org/

nmap.org/

first of all check all connectivity by pinging them and put weight age on ping. use command like this ping 0.0.0.0 -t -w 100000 and check are you getting any packet loss. second thing if you are using on board wireless card check the configuration it should be high frequencies one and if you using on board lan card also check weather you can upgrade it. check your wireless connectivity method and data strength i mean use proper chanel to broadcast network. hope it would sort out your problem.

Thanks