Been a few years since I messed with this, so bear with me.
You might try doing a search (Start button / "Search programs and Files") for yourMapsName_SR.map
So, If you left the default map name as "AUTOMAP" then you would search for:
AUTOMAP_SR.map
Two things of note:
1. If you installed Dominions to your program files directory, windows may be dropping files in a user directory of it's own creation.
2. Windows 7 has a notoriously horrible search utility, so just because it doesn't find it, doesn't mean that it is not there.
Failing the above, you might try installing Dominions and RanDom to it's own folder in the root directory (C
or the desktop, or wherever you are comfortable.
Hope that helps.