Can I have 2 versions installed?

Question

I would like to keep my iTunes 10.7 for use when I DJ, because it allows me to keep multiple playlist windows open as well as the main music library window open, all simultaneously.
However, I can no longer synch my iPhone (5, OS 7) because it needs the latest iTunes 11. Is it possible to have both installed, one that I would only use for synching some musi

Answer 1

As much as I hate to tell you this, find a new friend, because yours doesn't know what he is talking about. Here's how it's done, and it doesn't erase your drive to do it. To answer your second question, yes, you can do this on an external drive, but then your husband will have a slower system to work with, and that drive can never be disconnected or allowed to shut down.
To resize the drive do the following:
1. Open Disk Utility and select the drive entry (mfgr.'s ID and size) from the left side list.
2. Click on the Partition tab in the DU main window. 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.