I had previously found another solution:
Win7AudioSwitcher | Free software downloads at SourceForge.net
It can either autorun or be manually started and quit, gives a handy tray icon, and takes a 'mere' meg of memory. On my system it just works
out of the box. The suggested AutoHotKey may be the greatest but if you read the comments there you'll see there's a learning curve and possible script editing tweaks needed.