Running TCMD's help on the services desktop

Does anyone know why I can't run TCMD's help on the services desktop? I have a service running there and an instance of TCC too (as "nt authority\system", registered even!). If I try to invoke the help, or "start tcmd.chm" at the command line I get absolutely nothing. If I try to start it with RUNAS I get "Access denied" (to what, unknown). Likewise I can't start the service's .HLP file (and WinHlp32 is installed). But I can to **everything** else I've tried.