Playing nice with Windows on Wifi

I am experiencing an issue that I can't seem to get my head around.

The equipment involved:

Late 2012 model 13" MacBook Pro

Gigbit generation Airport Extreme

Sony Viao Laptop with Atheros mini-card running Windows 7

Netgear N300 router running custom-configured DD-WRT build.

The problem:

Every time I fire-up wireless on my MBP and connect directly to the Landlord's Airport Extreme base station, the WiFi on the girlfriend's Sony bogs out and starts dropping packets all over the place. The problem is intermittent and particularly noticeable under heavy bandwidth consumption such as during online games, browsing certain web-services, and Skype.

The workaround (thus far):

Hard-wire the MBP in behind a 3rd party router to act as a WiFi client in lieu of the MBP's WiFi.

The complexities and details:

1) I do not have control over the landlord's Airport Extreme which is on the upper floor of the house.

2) 95% of the devices on the router at any given moment are Apple products (Apple TV, iMac, iPad, iPhones, MacBooks) as determined by (Ze)Nmap.

3) An upgrade of the Wireless card on the Vaio is forbidden, as is any other update, change, or modification to the sanctified Sony device that can do no wrong.

4) I am the newest arrival in the suite and things were, "fine until you showed up"(sic), ergo I must prove to a graduate student in humanities (meaning ZERO tolerance for technical jargon that lasts longer than 20 second to explain) that the MBP is not the source of the problem.

5) An alternate Internet access source (Other than the iPhones) is not available at this time.

The hypothesis:

The MBP is potentially crowding out the Vaio, or possibly causing enough interference between it and the Airport Extreme so that the Atheros card in the Vaio gets 'confused' and packet-storms everything.

I've Googled all over the place and I have yet to find any articles, blogs, or posts that seem to indicate that this is anything but a 'one-of' problem.

My questions:

1) Where (if at all) would one go to 'turn-down' the WiFi signal on my MBP? (An experiment)

2) Has anybody experienced a similar situation, and if so; how (if at all) was it mitigated?

3) Could this potentially be an issue with the Airport Extreme and I am only chasing symptoms by dealing with the client(s)? (May require reclassification of my query to the Networking forum)

4) Recomendations for testing any of the above?