When you set the Home version drive as the first boot device in the bios you would have to disable any other drives. The question here is do you have a boot menu when pressing the F8 key at post time? That will list all ide drives including the floppy drive if you have that feature. Otherwise the F8 Windows menu will be the choice of startups like safe mode, safe mode command prompt only, last know configuration that worked, etc..
The bios will always default to the primary drive on a system. If you had installed one version to the secondary drive while the primary was plugged in the MBR(master boot record) and boot.ini file would have been modified automatically to give the option of which Windows installation to load when first starting the system.
One article that outlines how to edit the boot.ini file for dual OSing a system is seen at
http://vlaurie.com/computers2/Articles/bootini.htm Note that for dual booting the second drive instead of second partition seen as default there with "C:\ = "Microsoft Windows Me " at the end you would enter "D:\=Microsoft Windows XP Home" for the "D" if assigned that drive letter.