Airport Express to Extend Quest 2Wire Network

Reciently, I have been having problems going back as far as 6 months with a Quest 2Wire modem/router with my Power PC Imac. The signal strength was good at a location on the main floor of my house but would often drop out and not connect, unless I had either reset the modem or turn my airport card on and off.

Moving the machine upstairs to my bedroom, the connection was and is extremely week and often drops in and out with moderate lag that comes and goes.

As of today, I am using / testing out a 20in Intel Imac, with a better ...everything and the connection seems to be at least stable more than my 17in machine.

Also I bought an airport express hub brand new.

My questions are,

Can I use the Airport Express as a repeater to boost the signal from my 2Wire Quest modem/router? I already tried with no success to use the extend or WDS features of the Airport Express, as of now its connected to my modem with no problem any other attempt to try and boost my signal and I get yellow light each time.

I had tried hard reseting it with no sucuess, each time I connect the Airport Express trying to boost the signal its comes up with a yellow blinking light each time. As of now it is connected directly to my 20in Imac via eithernet.

Any help or input is well welcome.

thank you (>'.')>