Top Alternatives to SystemExplorer

Process Explorer is a Windows based utility to see monitor currently running processes.

htop is an interactive system-monitor process-viewer. It is designed as an alternative to the Unix program top. It shows a frequently updated list of the processes running on a computer, normally ordered by the amount of CPU usage.

Process Monitor is an advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity.

Task Manager, previously known as Windows Task Manager, is a task manager, system monitor, and startup manager included with Microsoft Windows systems. It provides limited information about computer performance and running applications, processes and CPU usage, commit charge and memory information, network activity and statistics, logged-in users, and system services.

Task Manager Free is freeware utility software that gives users a comprehensive set of tools to put them in full control of their computer.

GNOME System Monitor shows you what programs are running and how much processor time, memory, and disk space are being used.

Glances is a cross-platform system monitoring tool written in Python.

AtMonitor is an advanced monitoring tool for Mac OS X that displays system activity in real-time.

Resource Monitor a utility that displays information about the use of hardware (CPU, memory, disk, and network) and software (file handles and modules) resources in real time.

SpyStudio shows and interprets calls, displaying the results in a structured way which is easy for any IT professional to understand.