/join #Test does not work on my network. /join #Test does though and the only thing I notice is the colour code is included in the channel name in the window button and the channel name in all events goes black. This isn't a mIRC bug though, just an IRCd peculiarity.
while /join is being talked about - is there a type of channel you can join while disconnected from irc? one you can use to just check echo's and variables in?
Go to http://www.wircds.net/ and choose some windows IRCd, there are many help files usually in 'doc' directory. Or, if you have a shell account you can compile a real IRCd, it's not all that hard