Yet another frequently asked question. When using the BizTalk 2004 Administration Console, isolated hosts always report "Status unavailable" (see below).

 

 
BizTalk Server 2004 offers two kind of hosts: In-Process Hosts and Isolated Hosts. In-Process Hosts run in the same process as BizTalk and can be used to run orchestrations, run any send adapter and run the MSMQ or FILE receive adapters. Isolated Hosts can only run HTTP/HTTPS/SOAP receive adapters. From a pragmatic point of view, an Isolated Host is essentially an ISAPI extension running under the control of IIS. In BizTalk 2004, this ISAPI is called BTSHTTPReceive.dll. The documentation page "About Hosts" explains:
 

Isolated hosts primarily host adapters that must run outside of the normal BizTalk Server runtime process. For example, you use isolated hosts to host adapters for external processes such as ISAPI extensions and ASP.NET.

[...]

The status of an isolated host is always Status Unavailable. BizTalk Server does not access the status information for external processes.

 

So it is absolutely normal for an isolated host to report "Status unavailable". It should not happen for an in-process host.