I'm hoping someone has an idea of what's causing this annoying problem! We have a 20 user Windows 2000/XP (about 50:50 mix) network that ran with no problems until someone bought in a laptop with XP Home installed. The moment it connected to the network all connections and internet connection went down. Pinging any PC on the same switch worked, but not to a different switch. Looking at the lights on each switch in the path from this laptop to the router, the lights were flashing like mad. Disconnecting the laptop got the network back within 30 seconds. We took the laptop out of the network and thought no more about it until we put some new computers in. We now have 3 XP Pro PCs and 2 XP Home laptops that are doing the same thing. They seem to set each other off - 2 of the PCs were fine for a few hours until the other connected, now any of the 3 cause the network to stop working. All systems are using DHCP from a Netgear FR114P router, which then NATs to a broadband connection. Sounds a little like a virus, but we installed Norton, with updates, and it picked up nothing. Any ideas anyone? I haven't got a traffic sniffer, but if you know of a good free one that might give some clues. Thanks Kevin ___________________________________________________________ DISCLAIMER: This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to which they are addressed. If you have received this email in error please contact the sender or the Ionix IT Helpdesk on +44 (0) 1223 433741 _______________________________________________________________________