I disconnected the XP hard drive before Iinstalled Windows 7 on a new hard drive. I then reconnected the XP hard drive. The result was as expected.I can boot to either XP or Windows 7 from a cold boot by intercepting the boot process. Whatever system is run both hard drives are listed in Windows explorer. What I want to do is to be able to boot from one system to the other without going through the cold shutdown/intercept the BIOS @restart process. In other words is there a way (i.e. a run command) that will shutdown one OS and start the other

You can use bcdedit.exe, if you really want to get into it. You would need to add a {ntldr} section to BCD. Also whichever drive you want to boot first, needs to have an NT60 boot sector, and the BCD needs to be on that drive. Your Windows 7 drive has an NT60 boot sector but the XP drive has an NT52 one. You could change it with bootsect.exe.Otherwise, you can download a third party program EasyBCD, or re-install (or upgrade in-place) Windows 7, with the other drive attached.

If you can intercept the bios choice menu and lets you choose between earlier vresion of windows and windows 7 you would only need to change the default os values.If you need to enter bios setup you would also have to add ntldr.If the first scenario to switch to xp copy bcdedit.exe to system 32 of xp or it's already in there for 7 andType bcdeit /default {ntldr}to get into 7 typebcdedit /default {identifier value}where the value of identifier of7 can be found by typingbcdedit /vthis lets you switch back and forth quickly Proud to be an American.