Windows 7 - 2 os 2 hdd

I have win xp pro installed on one HDD and win 7 on another both os’s worked fine so I installed a dpdt switch to supply power to the hard drive I want to boot from, that also worked fine for a while and then when I switched from win 7 to xp the bios couldn’t find the hard drive so I plugged the power directly instead of through the switch and it worked ok again. I think the BIOS is getting confused as to which HDD it should boot from. My question is, would a boot disk help?

Thanks, Bob

Why would you want to jump thru all these hoops. Switching with the BIOS is so easy, I do that all the time.

Switching in the BIOS is easy when both operating systems are on the same hard drive not as easy with 2 hard drives or am I missing something here?

That may depend on your system. Some have a function key on the BIOS splash screen (often F10, F2 or ESC) where you can tap and directly go to the boot sequence screen and with a simple down arrow setting plus Enter you can set the drive you want to boot from.
But some other system do not have that convenience and you have to go via the setup screen which is more involved.
Check your BIOS splash screen what options you have.

If Compaq is anything like HP, and some of the specs look similar, should be able to just hit Esc or another key to choose the boot order, including boot from a USB drive. No biggie.

One would think that you are right. Unfortunately these buggers change things over time. I have an older and a very recent Gateway laptop. On the old one there is a boot sequence screen in the BIOS - in the new one there is not (maybe the Acer impact).
But on HPs and their derivatives you are right. It is ESC.

No, you cannot switch between OS's using BIOS when they are both on the same HD. It must be Windows-managed dual boot, which is complicated.

Hopefully you have the boot-sequence shortcut key WHS speaks of so that you can set a preferred HD to boot first and then easily interrupt it to choose the other HD. This keeps both HD's independent and easier to remove.