Computer kicked off internet by another computer

[bigbuffs]

So I've never heard of this happening before but I was trying to help my friend fix his internet problem today with no luck. Whats happening is every time his girlfriend turns on her computer (its a little acer aspire d255) it automatically connects wirelessly to their network. And as soon as it does it kicks his computer off the internet and it is a wired connection. I played around with some router and firewall settings and I got it so that his computer will reconnect after a while but it still disconnects every time the acer tries to connect. I am stumped here anyone know what the hell is going on? They said they tried it at there parents and the acer connects fine and doesn't cause any issues there.

Both computers running win 7 and he has a linksys router.

 

[kegobeer]

Are both computers trying to use the same IP address?

 

[bigbuffs]

I suppose that is possible. Would that be a setting in the router to obtain IP address automatically

 

[kegobeer]

Yes, it's called DHCP. It should already be turned on, but you should check it. It sounds like one of the computers has a static IP set that is within the DHCP range of the router (the block of IP addresses that the router will assign to the clients). Here's how the collision would happen:

The router has 192.168.0.100 to 192.168.0.199 set aside for DHCP
Computer #1 has a static IP set to 192.168.0.100 (this is done on the computer itself, not in the router)
Computer #2 turns on and gets an IP addresses assigned by the router. 192.168.0.100 is available and the router uses it.
Since the router has no idea that 192.168.0.100 is being used by #1, #2 get it and that causes #1 to be kicked from the "network".

Check both computers to see if one of them has been assigned a static IP address. If it has, then either stop doing that or choose an IP address that is outside of the DHCP range.