Others here have tried getting key in earlier OS and dropping it into Win7 - it doesn't work.
v11.2 can work in Win7, several here have managed that - I've also taken the tips from here to get a number of other people up and running with v11.2 on Win7. In most cases (I won't say all) set compatibility to Vista SP2 seems to do the trick, it isn't entirely clear but changing the PC name may help in some cases (as long as you have spare key allowance remaining). The graphics drivers which ship with Win7 may need updating to allow correct functioning (but I think that's mainly for when you get beyond licensing).
Check that you haven't reached your limit for licence keys.
[EDIT - BTW, I can understand Alibre's position. v12 was the first version designed to be Win7 compatible, if you choose to try to run v11.2 on Win7 you are technically working with an 'unsupported operating system'. ].