In the “Windows Client Operating System Management Pack Guide for Operations Manager 2007” you can read about monitoring Business Critical Clients. But even if you import this management pack, and add your business critical workstation to the “All Business Critical Windows Critical” group you will not get an alert when the workstation are unreachable for example disconnected from the network.
If you look at the “Computer Not Reachable” monitor you will see a default override that disable it for Computer Clients. The same thing for the “Health Service Heartbeat Failure” monitor. If you then add your workstation to the for example All Business Critical Windows Client/All Business Critical Windows XP Clients” group and then create a override that enable “Generates Alert” for the two monitors for this group, you will get an alert if they are unreachable.