Setting wireless service to share conection

I have some computers at home. 2 laptops (1 with pcmcia wifi adapter 1 with built in adapter) and a desktop (usb wiufi adapter)

I have a DSL modem/router (single port comtrend 5071) conected by ethernet cable to the computer.

All computers are running Windows OS (SP Pro, XP home and ME)

Currently I'm moving the ethernet cable from one computer to the other to surf on the web.

I would like to have access simultaneously or at least without having to move the conection.

I've bought a DWLG700AP from DLink following shopkeeper advice to achieve the goal.

I've tried unsuccesfully to connect the Access Point to the modem router. I've followed all instructions and troubleshooting sections of the manufacturer. Even I tried to set up the AP directly conecting it to the PC through ethernet cable.

In addition to any suggestion (Ping from system answer is request time out) I would appreciate advice on the option itself. I wonder if it would be better to buy a wifi router (modem and so on) and get rid off the comtrend 5071.

I know questions are very basic but I'm a bit lost and short of free time to spend on that fight.

Thanks in advance

Have u installed the ethernet cable from modem to router on the right port ( wan port )???
please give me detail bout your os version, sp and if possible hardware spec??