Nice.
WriteMonkey does look like just the ticket.
To get it to start up like you want, see if it takes command-line parameters and stick that in your startup script.
Q10 looks similar, but less features:
http://baara.com/q10/Come to think of it, if you're still using XP you could even go with a minimal Explorer replacement like
LiteStep or
Blackbox, but that's probably more work than it's worth.
If you're using Windows 7, it's recommended to use the
Omar installer (LOSI doesn't like Win7...)
I found a few similar editors for Linux, all more or less based on
WriteRoom for Mac OSX:
jDarkRoom
http://www.codealchemists.com/jdarkroom/Written in Java, so it runs on Windows natively and the Linux version interface is Desktop-Environment agnostic.
Has a 'no delete' mode as well.
Last updated May 2010.
PyRoom
http://pyroom.org/Requires GTK, dunno why, there's almost no interface...
Not much feature-wise but soon will have plugin support.
Last updated March 2009.
TextRoom
http://textroom.sourceforge.net/Requires Qt.
Sports a TON of features, including 'flow mode', typewriter noises, scratchpad, and a Mindmapper flowchart thingy based on
Flo which looks quite useful.
Updated recently; as in Yesterday...
Windows portable version available with integrated libraries.