In 64 bit window can i use cs3 32 bit

Gnerally speaking, the majority of 32 bit progams can be run in 64 Bit windows 7.
a few "older" programs may need to be run in "XP" compatability mode. Have run some programs that are from Windows 98 days.

What will not run is Older 32 bit programs that contain 16 bit code (quite old programs.

Bottom line as others have said, CS3 should be fine.