"POST" is an acronym for "P
est" and it refers to the sequence of events that your BIOS performs just after you apply power to your system. This includes such things as testing the location and amount of memory. identifying some of your system resources, sequentially checking the boot devices in the order you have set them up, and things such as this.
To set up my system for dual boot, I simply set the BIOS to read the ODD first, then HDD1. I inserted the Win 7 installation disk I had created from the ISO file, powered up, and let events unfold as I montiored progress. The BIOS creates the bootstrapper screen to resolve the fact that there are two (or more) places from which to load an OS. I didn't have to set anything in the BIOS, the bootstrapper screen appears almost immediately after power is reapplied after installation.
I already had Vista 64-bit on the 640GB drive, so when I installed Win 7 7100, I made sure to select the second HDD as its home.
Be careful about installing a virus program in Win 7. When you do a scan, it will not know to differentiate between the two drives, so make sure you know what you are about to scan. I use McAfee (because it is free from Comcast) on the Vista 64 side and Kaspersky (Beta, also free) on the Win 7 side. I limit the scope of each to the drive on which it resides.
I am not by any means an expert in any of this. I have just been cautious and lucky ... so far. Good luck.
I forgot to add in my last reply:
If you need to tweak your bootstapper, download EasyBCD 1.7.2 from neosmart.net
to your Vista drive, it is free and useful, and can probably help setting up your dual boot the way you want it.