Funny because I read everywhere, like Tom's hardware, that it is on the same disc. The activation code applies to both 32 and 64 bit as long as it is the same version of windows 7.
IF you could show us a weblink or thread for this, it would be great.
So far as I know, and I have used all the versions of Window 7 since Jan of 09, the 32 bit and the 64 bit came as separate downloads or discs.
Now on some of the P2P websites, there are available some "hacked" installs called: AIO or All In One, where the two versions have been combined.
I'll do some further investigation on this.