If you have a blue screen, or the user interface is locked and you can't even get a response if you press Ctrl+Alt+Del, then it's almost certainly a hardware or driver problem. Check the Resource Kit or search at Microsoft.com for the blue screen stop message code for some troubleshooting help. Make sure you're at the latest patch levels and that you have the latest firmware for your hardware.
If the Web server stops serving pages but everything else works fine, you probably have an application with a memory leak. This is very, very common, especially with ASP 3.0 applications. The best way to fix this is to clean up the application's code or write in it a more reliable environment (for example, rewrite it using ASP.NET). Alternatively, you can keep running the unreliable ASP 3.0 application by upgrading to .NET Server when it's released, because IIS 6 will automatically restart your Web applications when they fail. Or you can reboot the server every night.
This was first published in January 2003