Running two versions of Simply Accounting on one computer

It can't be done.
Students should be able to navigate the various versions with ease, since the user interface hasn't really change much. But Sage only allows one per PC.

Unless you follow this recipe.
Enter Virtualization. (VM)

1. I installed virtualbox because it is easy and my PC is old (most use VMware Player, see below)
2. I pressed New and created a Virtual Machine. 
3. I installed Windows XP SP2 from a CD with a second licence key.
4. Downloaded Simply Accounting 2011 to a USB
5. Attached the USB to the Virtual Machine. (lower right of Virtual Machine window) (It seems you can only attach a USB to one machine at a time... Virtual or Physical)
6. I installed Simply Accounting 2011 in the Virual Machine Window.

 That way you can handle files from any source. Whew!

VMware Player FAQs: Free Virtualization to Run a Virtual PC on Linux or Windows:
"VMware Player is the easiest way to run multiple operating systems at the same time on your PC. "  Warning: Hardware Virtualization required.  This guy seems nice:

Test your PC using: SecurAble http://www.grc.com/files/securable.exe

On most systems it is disabled by default for security reasons. To enable it, you have to change the corresponding BIOS settings. That is, you have to enable hardware virtualization and the NX-bit (AMD) or the XD-bit (Intel) respectively.

OR

Try Oracle virtualbox.org or other Alternative free virtualization-software if your PC lacks Hardware Virtualization. (don't they all!).  

Then install Windows XP G/D a free windows simulation or install a full windows XP if you have two licences.  Others available in the VMware Virtual Appliance Marketplace.

Then install the simply accounting student 2011

Presto!