I am still at a loss on this because a firewall will block TRAFFIC, not the computer operation trying to USE that traffic. In the OP you were looking to block the CPU interruption caused by anything trying to poll. The firewall isn't going to stop that. It is only going to deny the actualy traffic. The CPU will still be interrupted. To stop any IRQ you will need to turn your network connectivity off, shut off anything that ever updates, like anti virus software, real player, adobe, office, windows updates....

Also, if you DO set it up that way, you will get an even bigger interruption when the firewall puts up a message saying "SOMEONE TRIED TO ACCESS YOUR COMPUTER BUT WE GOTCHO' BACK AND STOPPED THEM!"

Open up task manager, go to the performance tab, let your system sit and settle to what you think is a totally idle state, and watch how it still uses cycles. Then nudge your mouse and see the cycle use go up slghtly. It will go from 2% to maybe 9%. And that is from moving your mouse maybe 10 pixels. Imagine how many CPU cycles would be used for a firewall to receive a packet, analyze it, reject it, and then display a message which it retrieved from the hard drive storage, sent it through the CPU to the RAM, from the RAM to the video bus, through the card and to the screen.

This is why it was suggested by a few people that you have a pristine computer if you are that concerned with your CPU getting an IRQ for an update poll. The OS, minimum video and sound drivers, and BIAB. Period.