Dual boot Vista and Windows 7 on seperate HD's

Hi everyone

I need a little help with dual booting. I am running Windows Vista 64 bit (default OS) on one HD and Windows 7 RC 64 bit on another.

I want to dual boot these HD's/operating systems. Most of the sites I visit only tell you how to dual boot a single HD with multiple partitions and never explain how to dual boot from seperate HD's. They also don't tell you how to go about setting up the dual boot, they only tell you which programs to use (Vistaboot pro and Easybcd)

Please help

Thanks

My system

ASUS M4N72-E Motherboard
AMD Phenom II X4 940 CPU
MSI GTX285 OC GPU
Corsair TX750 PSU
4GB OCZ Reaper HP memory (2 X 2Gig kit @ 1066Mhz)
Samsung Syncmaster 2243bwx LCD
Zalman GS1000 Black case