I've been running into the "mc is not recognized as an internal or external command" error that's mentioned in the Building Poco FAQ while trying to build Poco/trunk
I took a stab at tracking it down and I think it's really a case of a very misleading error message instead of a path or missing MC.exe problem. I *think* what's really happening is that after the Message Compiler runs, it's deleting the pocomsg.rc and pocomsg.h files from the Foundation/src directory. The next time you try to build, Visual Studio says it can't find MC.exe when it really means it can't find the 2 pocomsg files.
I'm running VC Express 2005.... here's the steps to reproduce:
1. checkout the Poco/trunk
2. build Foundation...any configuration
3. check Foundation/src and see that pocomsg.h and pocomsg.rc are now missing
4. rebuild Foundation and you'll hit the 'mc is not recognized as an internal or external coomand " error message.
If you re-add the 2 files then the build will work again.