I don't know if somebody already resolved this problem but I just happened to figure this out.
Except you didn't read the title.
We don't want to know how to choose what program 'opens' ... (that's the only thing you CAN do in Win7..)... we want to know how to assign other actions...
Like edit, view, preview,
or add custom ones like
'edit in photothing'
'edit in mspaint'
edit in my finger painting app'...
etc...
Anything but open is difficult or impossible with Windows 0-- where once it was trivial.
MS is really dumming down and removing features as they put out new version -- AND raising prices...
If you look at everything you got in WinXP-Pro -- that's the equivalent of what they call Win7-Ultimate today. You go a level down and you are missing domain security (which I use at home), OR you lose media play ability -- both things XP had ....
But wait, for all these fewer features and greater cost -- you also get a 15-30% slowdown on all OS related functions!
Remember the good old dialup days when there was a 'lag' between when you pressed your keys and they were echoed (because they had to go to the remove site which did the echo?)----In Win7 you get that same feeling -- keys are lagged as they are shipped off
to someplace for inspection...
Remember type-ahead? Win7 drops keys regularlly -- so can't rely on it...
And lets not forget several people's fav -- lack of home-network searching!.... Sure if you buy MS SErver and run it at home, you're set, but any other network drive.... they gave us the pooch.
And now they are blythely moving on to Win8?? Gawd ... I see how Vista users really felt like suckers. MS, what's wrong with you? Are you determined to kill the **personal computer**??
Leaving the above orignal content.
But I get updates on this and don't understand the whiner's upsets -- the question was answered BEFORE this follow up pose by Shawn Keene on July 13, 2011, The fact that my follow up got moved up under his was because others agreed with my "grumblings".
But Shawn points to the below (http://izt.name/apps/types/). So if you want to solve your problems, learn to read, as his answer was posted before my followup, AND is above mine in the reading order.
Types
Types is a simple Windows utility that allows you
to add and remove file types, set program associations,
change icons, edit context menus and other properties.
Download

Types 2.1.1
(196 KB installer)
Nov 29 2012 .Net 2 or 3 required (NOT 4+)
Localize
Place language files either next to the downloaded Setup.exe
or into the installation folder (default: C:\Program files\Types).
Press F1 to select your language, then restart the program.
Language file template