Can’t install Win7 64 bits on Vista

Hi all!
I failed to run the set up of Windows 7 64 bits. And an error emerged which reads -”Cannot install Windows 7 on this version of Vista.
Now I understood that it is because I’m using 32 bit OS. I need suggestions on ways to clean install.
Please also help me with the following issues: How to format C: on vista?
Is there any possibility for 7 to run at startup after formatted derives?
Help will be appreciated.
Thanks.
