I think that WhatsUP Gold is not available anymore, It is now WhatsUp Pro. I use it and it is very good. I also use a network monitoring software called KS Hostmonitor (http://www.ks-soft.net/), It is a very powerful network/server monitoring tool worth a look at. Both have powerful reporting tooks, and can send notifications and alerts. Hostmonitor can monitor all sorts of server availablities and alert when thresholds are exceeded such as ping, http, https, ftp, dns, service/processes failures as well as warn when drive/folder space exceeds a threshold, warn if a file changes. I use it to monitor numerous configuration files for changes such as the config file for my firewalls and GPO’s. It can do much more.
If you have a large network or one like mine that is a must that it is availabe 24×7, and budget it allows it. I would setup a little NOC using both applications. The cost of both programs together realy is not that expensive.