32 bit to 64bit...

I currently have Win7 32 bit and I want to upgrade to 64bit...I read that this cannot be done without formatting the HDD...
But I have another hard drive which is clean...Can I istall the 64 bit version on the other hard drive via the 32 bit system?I mean putting the CD on and then manually installing Win7 x64 on my other HDD?(Like installing games etc) 

So you want to dual boot 32-bit and 64-bit? Should work fine, but I'd unplug your current hard drive first just to make sure you don't accidently overwrite your current drive.