I think they should be placed on Documents\My Games\Company of Heroes\WW2\Scenarios... could someone else confirm this
.
C:\Documents and Settings\[your user name]\My Documents\My Games\Company of Heroes\ww2\scenariosThat's for Windows XP.
But that's the easy, and the more than imperfect way to do it, since, unless you place maps into
[CoH main directoty]\Eastern_Front\Archives, and enlist the name of the map in
eastern_front.module (
[data:common:01] part), there will be problems with savegames and replays, if my memory doesn't fail me.