CallZap is available on a 15-day, free to try basis and is supported in Windows systems, including NT, Me, XP, 98, and 2000 versions of Windows. Developed by Softwarevolution, this application is intended to help users to monitor and block unauthorized and unwanted calls, automatically. This utility uses the computer’s modem and caller-ID service to recognize unauthorized numbers that needs to be blocked. You can use this tool to create a list of names and numbers that needs to be blocked. Any calls from the numbers in this “block list” are terminated immediately. You can also block calls from unknown numbers and private callers, using this tool.