consolidate vista/win7 onto one drive

Hello,

I currently have vista and win7 as two independently installed OS on two hard drives. I choose which one to boot into by going into BIOS and change the hard drive boot sequence. Now I want to put them together on the vista drive and use BCD to choose the OS. I already freed enough space on vista drive for a win7 partition. Should I create a primary partition or an extended partition? Or it doesn't matter? And after I copied win7 partition to this newly created partition, what should I do to create the correct BCD?

The only reason to have an extended partition is if you want more than 4 partitions in total on the HDD.
You can have 4 primaries, or 3 primaries and an extended inside which you can put as many logical disks as you want.
If you need 4 partitions or fewer, keep them all primary.
If you need more than 4, try to keep Windows partitions primary, and use the logicals for data (or Linux which is far less fussy about where it boots from)
Windows (from XP onwards, not earlier) can be installed onto logical drives, but not booted from them.
The Windows boot files must be on a primary, so for simplicity, keep the whole OS on a primary unless you have no choice.
Vista on your partitioned HDD will be "system". When you clone W7 onto the new partition, just boot Vista, install EasyBCD 2.0 latest build, and add an entry to the BCD for W7, pointing it to whatever letter Vista sees the W7 partition as.

(You don't need to clone W7 onto the Vista HDD though. You can just add Vista to the W7 BCD, or W7 to the Vista BCD and dual-boot them without going into the BIOS, with the OSs on different HDDs.
You can also temporarily override the BIOS boot sequence by a hot key normally. On my ASUS mobo it's F8 before the BIOS splash screen to override the boot device, F8 afterwards to enter the extended boot menu)