Your question isn't clear, but I'll make a guess at what you're asking.
After Effects CS5 is a 64-bit application. It requires a 64-bit operating system and 64-bit processor. There is no 32-bit version of After Effects CS5.
After Effects CS4 is a 32-bit application.
CS5 Production Premium & Master Collection (Windows) include Premiere Pro CS4 & After Effects CS4: http://bit.ly/bS5O8P
What the man said... CS5 is 64bit only.
What's the rationale behind including CS4 apps in the CS5 suite? CS5 requires a 64-bit OS, period. It's on the box. If the system requirements were 16GB RAM, would Adobe include free DIMMs in the box? This seems just as silly.
For new users (not upgraders), it seems like Windows users are getting more flexibility and compatibility by offering them more software than Mac CS5 buyers.
> What's the rationale behind including CS4 apps in the CS5 suite?
The only major applications that are strictly 64-bit applications are Premiere Pro CS5 and After Effects CS5. If someone with a 32-bit operating system wanted the CS5 versions of other applications (such as Illustrator, Flash, Soundbooth...) and bought the CS5 suite, we wouldn't want them to be completely without After Effects and Premiere Pro.