Ok I have solved this but it was a wierd one.
It was a cabling mess up on the dirty side of the network it would have been easy to find if the XP and Vista machines also stopped working but they didn't thats what through me off initially.
I have no idea how this can be possible but I had the switch for the vista xp and windows 7 machines connected to the wrong side of the Router and the DHCP server was on the right side of the Router.
This means that the Vista and XP machines were getting IP addresses through a Router and the Windows 7 machines were not
I don't know but the last I heard this was not possible broadcasts can't go through routers unless they configured to let them through and I have not done that
Ah well I am happy its solved
Thanks for all the replys
It was a cabling mess up on the dirty side of the network it would have been easy to find if the XP and Vista machines also stopped working but they didn't thats what through me off initially.
I have no idea how this can be possible but I had the switch for the vista xp and windows 7 machines connected to the wrong side of the Router and the DHCP server was on the right side of the Router.
This means that the Vista and XP machines were getting IP addresses through a Router and the Windows 7 machines were not
I don't know but the last I heard this was not possible broadcasts can't go through routers unless they configured to let them through and I have not done that
Ah well I am happy its solved
Thanks for all the replys