64 & 32 bits on a same system??

Why would you want to do that?

If you want to try it, make sure to partition the drive.

Most if not all 32 bits applications will work in 64 bits as well. The few applications that won't work in Win7 x64 probably won't either in 32 bits so you are better of using Windows XP virtual PC for that.

32bit first next install 64bit = 32bit became Old window (cannot work) & first intall 64bit to 32bit = 64bit Oldwindow not working

Install 64bit in system there 2 program data for 32bit & 64bit all work good !
if 2boot 1HDD must different Partition.

why.?
win7 ultimate has xp-mode 32-bit or 64-bit.
that's all you need.

Yes, you can.

Make two bootable partitions on your hard dreve, then install 32 bit on one, and 64 bit on the other.