Hello and welcome to Bleepingcomputer.
Your question is can you put two different operating systems on the same computer on different hard drives.
The answer is yes.
When you install the OS off of the installation disk it will ask which drive you wish to install the OS too, it might list the drive by its hardware ID number.
That drive will be listed as C: and Windows will offer to install to C:\Windows
If you have both drives installed in the computer when you install the second OS on the second hard drive and the first hard drive is still installed, the second OS creates a boot menu on the first boot drive. Sometimes if this option gets corrupted for any reason down the line, one or both OSes becomes none bootable. Even if it is still listed in the list of options at boot up. The corrupted OS won't boot, in all likely hood, you'll just see a curser blinking on a blank screen, that never goes anywhere, while the other OS still boots successfully.
This is caused by a corrupted Master Boot Record at sector 0, sometimes it can be repaired and sometimes it can't and requires a full reformat of the whole drive to fix this corruption.
It is better in my option to remove the first drive and install on the second drive independently set as a master drive, then change to a slave once install is complete and choose each drive as the first boot drive through the BIOS boot option in your BIOS setup utility and switch the drives around that way.
It also prevents problems down the line if one drive fails or is removed from the system.
Windows OSes usually do not recommend dual booting computer systems for the same reasons.
Edited by MrBruce1959, 04 July 2010 - 11:32 PM.