My router stops working when a windows computer tries to connect

I have a Linksys WRT110 router in my apartment, which normally works fine, it just runs slow (it's pretty old, so I'm not surprised). However, whenever a computer running Windows tries to get on if there's another computer or device already using the internet, it stops working for everyone.

My 3 roommates and I all have Macs, so this isn't normally a problem. However, I'm looking to get a new computer soon and I want to get a PC. Has anyone here ever heard of anything like this happening? Router working fine with computers running OS X, but the instant a Windows machine tries to get the wifi, the internet stops working for everyone. This also happens if I try to use a Windows machine when the Xbox is turned on, which is connected to an ethernet cable directly to the router.

It's the Xbox thing that makes me think this is a router problem. Any suggestions, or should I just buy a new router?