MongoDB on Windows should I think come with clearer advice that it really needs to run on a separate server.
Because MongoDB can’t limit its memory use, and can expand to use all available memory, it would appear unsuited for use as part of a desktop application, or a “shared single server” web-based system.
A separate physical or virtual server is required, unless your using Windows Server 2003 or 2008 with WSRM - http://bit.ly/tQs63L
Source: bit.ly