I need to check the disk space in a number of remote systems (Windows 2000) and have to sent a mail if the space is below a particular level. How can this be automated? What script can be used?
One option would be a system monitoring tool, such as Nagios.
Basically, what this will do is continually interrogate your systems, and alert you to anything you set it to (disk-space, CPU usage, page-faults, etc.). As a bonus you get a lovely web-based interface which lets you see your system status at a glance.
Note that you will need to enable remote WMI querying on each target system, or install an "agent" on each system.