[SteelTrap]

Or you can set up a Scheduled task that runs every 11 hrs or so using a script containing this:

ipconfig /registerdns

This will renew all your DHCP leases and re-registers DNS names. If that doesn't work, try:

ipconfig /release
ipconfig /renew

[erinjohn]

Sounds as though your siemans router is resetting the DHCP on you without updating the PCs. Can you still ping the ISP from the Router after the 12 hours? That would definitely rule out the ISP. You can set the IPs on the PCs to be permanent as long as they are in the range of the LAN interface on the router. The outside int on the router does not matter in this case. Usually the inside int on the router is 192.168.1.1 or some such. I have mt PCs set to 192.168.1.100 255.255.255.0 through 192.168.1.200. YOu will not have the DHCP problem after that.