Windows 7 - Multi-boot system

I already have xp and Windows 7-64 on my computer. I have 4 internal HDD's and am thinking of adding third OS, Windows 7-32. Since they would be on the same computer, will I be able to activate the Windows 7 32-bit version?

Yes as long as its on a different partition or drive.

You can't use the same licence to install 7 twice. If you have another licence, choose the right hard drive and go ahead. Better yet, disconnect all your hard drives except the empty one when you install 7.

Even on the exact same hardware? If it was on a separate HDD, yes, but I can't see why it wouldn't work on the same drive. Surely Windows would see it as a reinstall on the same hardware.

You might end up in a loop where each one has to be reactivated. I think this is one you need to call Microsoft and ask, and then post back and let us know what they say. It's reasonable that they would allow it since the two can't be used at the same time, but definitive word can only come from Microsoft on this.