I recently upgraded from Snow Leopard to Lion and now some CDs I use for school do not work. Can I create a partition to run both Snow Leopard and LIon or does it only work to run windows? How do I do this?

Question

Getting a new CD from publisher is not an option as they would want me to pay for a new one and they are pricey.  If possible I would prefer to keep my upgrade to lion but would go back to leopard if there's no other option.

Answer 1

You can add another partition on which you can install Snow Leopard. If you do, however, you cannot use Boot Camp Assistant to install Windows. Just so you know.
To resize the drive do the following:
1. Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
After the main menu appears select Disk Utility and click on the Continue button. Select the hard drive's main entry then click on the Partition tab in the DU main window.
2. You should see the graphical sizing window showing the existing partitions. A portion may appear as a blue rectangle representing the used space on a partition.
3. In the lower right corner of the sizing rectangle for each partition is a resizing gadget. Select it with the mouse and move the bottom of the rectangle upwards until you have reduced the existing partition enough to create the desired new volume's size. The space below the resized partition will appear gray. Click on the Apply button and wait until the process has completed.  (Note: You can only make a partition smaller in order to create new free space.)
4. Click on the [+] button below the sizing window to add a new partition in the gray space you freed up. Give the new volume a name, if you wish, then click on the Apply button. Wait until the process has completed.
You should now have a new volume on the drive.
It would be wise to have a backup of your current system as resizing is not necessarily free of risk for data loss.  Your drive must have sufficient contiguous free space for this process to work.
Boot from your Snow Leopard DVD and install on the volume you just created. Be sure you set the new partition as the target for your Snow Leopard system.