Your question is a little muddled by grammar mistakes but if I'm reading your question right. A 64-bit OS won't install on a 32-bit processor at all.
Well, I take that back. A poorly written installer may let you install the OS but you wouldn't be able to run it. The Windows 7 install and all Linux distros I've ever used properly detect the processor during the install and won't let you install a 64-bit OS on a 32-bit processor.
warrenkopp is correct, by the way. Every supported processor for the Inspiron 1720 is a 64-bit processor. You'd be hard-pressed to find a system manufactured in the past 3 years that ships with a 32-bit processor.