Richt-click the shortcut or executable (fleet command.exe in game folder) and select 'properties' (bottom of the list).
Go to the 'compatibility' tab.
Check 'disable desktop composition'; this will disable Aero which tends to interfere with older games.
You could also try 'disable visual themes' and selecting a compatibility mode (the one with the list, 'Windows XP' should work).
If that doesn't do it, try enabling more options and/or setting an older OS in that list.
I can run it on 4GB RAM and a quad-core with Win7 64b, so it should work. Think I still sometimes had flashing in the menus, but nothing bad enough to keep me from playing.
