You have a Thinkpad T410. You use a second drive in an ultrabay to boot from and run applications that you do not want to run on an internal hard drive. Can you run Windows 7 in a 32 bit format on an internal drive and as a 64 bit format on an ultra bay drive without any issues?
You are currently running a 32 bit application of Windows 7 on both drives. You want to know if it is safe to install a 64 bit version of Windows 7 on a drive in an ultra bay before you try it. Yes it is as long as you take out your main drive before installing Windows 7 64 bit on your ultrabay hard drive.
Here is how to set it up. Remove a main hard drive from a mainbay. Install a second hard drive in that ultrabay.
Install an operating system in this case Windows 7 64 bit on that ultrabay drive. Put that mainbay drive back into a main slot. Now when booting up, if you do nothing it will boot to a mainbay.
When booting up, you can press an F12 key, it will bring up a boot menu, giving you a choice of which drive to boot into. Then at anytime, you may remove that ultrabay drive to use an optical drive, or ultrabay battery without having to make any adjustments to that system.