All computers connected to the router randomly disconnecting...

There are four computers in the house which are connected to the internet
through our DLink router. The three which aren't running vista can connect to
the internet fine and stay connected. But, whenever the computer that is
running vista connects to the router, all of the computers intermittently
disconnect from the network. This started happening early October and we've
been reluctant to act on it until now. We've researched similar cases and
what they've done to fix it and done so. Nothing has worked yet. I have
diagnosed this issue and sent the reports to Microsoft several times but have
not gotten a solution.
Any and all information on how we might be able to fix this problem would be
greatly appreciated. Everyone in the house is becoming extremely frustrated.