Received this notice via e-mail from Comcast, my ISP provider. Firstly no one in the household has downloaded the file they said was downloaded. Ran a search on all computers and did not find anything. Should I send a counter-notice or just disregard ?

Have you called them and asked them what is going on?

Example: I recently got a notice and it said about foreclosure. As it turns out because of changes in the law they sent that notice to everyone.

This may or may not be the case. But if it came from your provider and not from the copyright holder then its most likely a blanket one sent to everyone. But anytime something like this is mentioned call them to find out.