I\'ve got a project where I\'m hitting a bunch of custom Windows Performance Counters on multiple servers and aggregating them into a database. If a server is down, I want
The "Full-Blown" option would be to install a monitoring tool like SCOM (System Center Operations Manager), this has an SDK you can use to query SCOM for (performance) and maintenance information avout machines being monitored. Might be a bridge to far though....
Telnet is another option. Try telnetting to the target machine to see if it responds.
Create a small Windows Service that you install on your target machine, have the sys admin stop it when they perform maintenance on the target machine (just use batch file to net stop / net start the service)