I used up the free trial on my PC a while ago, so I don't know since I haven't searched. The reason I ask is because I guess there are few different preference options for a PC and a Mac. I have Illustrator on my PC and I had the option to change the key command for undoing. When I use the program at school in the Mac computer lab, I do not have that option.
I'm interested in buying Photoshop, so I just want to know if the way to add multiple undos can be adjusted on a PC. I know it can't be on a Mac.
Illustrator and Photoshop on my Mac allow me to change keyboard shortcuts including Undo. Perhaps your school has configured the CS6 apps to not allow changes by students. I'm quite sure you'll be able to change the shortcuts in an installation on your own PC. In any case, you really should take the opportunity of running the free 30-day trial on your PC before parting with any money.