Two wifi routers, two computers, an Xbox and lotsa headache!

For the past two months I've been trying to get rid of these nasty green Ethernet cables snaking their way from the living room to my home office with the help of two wireless routers. My hair pulling during these past months have made me partially bald, so my wife has requested that I instead find someone who knows how to do this. So here I am.

Here's my setup...
Home office:
- 2 x desktop PCs with normal Ethernet ports.
- 1 x SMC barricade g, broadband wifi router (SMCWBR14T-G)
The two desktop PCs are connected to this router.

Living room:
- 1 x Xbox
- the ADSL modem from my DSL provider
- 3COM OfficeConnect wifi router, connected to the Xbox and ADSL modem

Other:
- I also got 2 laptops that needs to use the wifi network.

The 3COM router has worked fine, so I have a wifi network working that connects all the computers to the internet via the ADSL modem. But I've been using two Ethernet cables to go from the 3COM router in the living room to the two computers in the home office. I'd like to get rid of these two cables.

The solution I was suggested was to buy an extra wifi router, place this in the home office with direct line of sight with the 3COM router, and setup the same SSID on the two routers. The two home office computers could then connect to this new router and the network via two short Ethernet cables. No more cables between the living room and the office, yeah!

Unfortunately, all the instructions that came with the SMC router are practically useless as they assume that you're only going to use this router as the main router that connects to your ADSL modem. So I can't figure out how to do this setup.

Any suggestions?