Have you rebooted the Windows PCs?
When their IP address expires, they try to renew it. If the network is down (the power blackout) they assign themselves a new and random address in the range 169.x.y.z. This may be what has happened in your case.
If so, your Windows PCs are on a different logical network from your servers.
A simple reboot will fix it.
BUT you can do it without rebooting by opening a DOS box (Start/Run/cmd) and typing "ipconfig /renew" <Return>
Hope this solves it for you.
Cheers
Ian