Simple Server Monitor 2.0.5
Simple Server Monitor is a powerful, yet easy to use network server monitoring utility. It allows you to monitor the status of your servers and web applications from your desktop. Simple Server Monitor runs as a Windows Service with GUI monitoring console. When a monitor fails, you are notified by a pop-up message, an e-mail alert, and/or a sound alert. Charts monitoring performance. Supports Ping, HTTP, FTP, SMTP, POP, IMAP, and Custom monitors.

PA Server Monitor 3.3
PA Server Monitor is a Windows service that monitors the health and availability of Windows servers, network services (on Windows, Linux and other operating systems), and devices. No agents are needed to monitor remote servers. Also includes rich reporting on most monitored resources. PA Server Monitor can watch: Event logs, CPU, memory usage, free server disk space, changed files and directories, running Windows services, and much more.

DEKSI Network Monitor 5.3
DEKSI Network Monitor is an advanced, powerful, and feature rich tool that monitors servers located on your LAN, WAN, and the Internet. DEKSI Network Monitor will allow the Administrator to increase the reliability and productivity of your corporate servers. Windows 9X, NT, 2000, XP, 2003 Server , Vista compatible and can monitor the servers with any operating system (Windows, Linux, Unix, etc.)

CommandCenter-NOC 6.0
The CommandCenter NOC performs network monitoring with a powerful polling engine, keeping close watch on your Windows servers, Linux/UNIX servers, network devices and applications. It can also continually monitor the performance of your network using configurable thresholds. If an outage is detected, or a threshold is crossed, the appropriate staff members can be alerted with e-mail or pager-based notifications.