Basic Q re: network set-up

[#1]

Hi all
Something has gone wrong with my network set-up.  I have a very simple set-up:  Wireless Router connected via wi-fi to Laptop and XBox360.
However, currently I can only connect to the router with one device at a time.  So, if I'm playing on the XBox and my wife fires up the laptop I lose connection all together on the XBox.  The only way to reconnect the XBox is to turn the laptop off.
Any idea what setting I've inadvertently changed?  It used to work just fine!
thanks
Rich

[#2]

Are you using DHCP on the network?

[#3]

Thanks for the reply
Embarrasingly, I don't know what DHCP is. 
Wikipedia has given me a bit of an overview - but what specifically do I need to do or change to figure this out?
Sorry for not knowing 
rich

[#4]

What router do you have?

[#5]

Quote from: aphemia

Embarrasingly, I don't know what DHCP is.

I wouldn't be embarrassed - I've met numerous IT staff who have no idea what it is - your overview has already put you ahead of them in the knowledge stakes!

Essentially, as you have read, DHCP is what allows your router to automatically configure elements of your client machine connection (Dynamic Host Configuration Protocol)
The issue might well be that your router is automatically issuing an address to one machine, which another machine has manually been configured to use.
Because each IP address needs to be unique on a network, this is the most likely cause of your issue.
The next steps are to alter your config slightly to prevent this from happening again.
As Adie says - tell us your router make/model, and we can help you out with changing the settings appropriately.

[#6]

Thanks guys
Sorry for the delay.  I'm just getting round to this!
Router is Netgear DGN2000.
By the way, I get the same problem in reverse.  If I'm on the laptop and then fire up the xBox, the laptop disconnects!