I bought a copy of Parallels and ordered the back up CD with it. The software has been working fine, but I want to install Ubuntu onto my hard drive. The problem is, I messed up my MacBook's hard drive somehow, so OS X won't let me partition it. So I have to erase the HD and do a new install of everything. The only software I have a concern is Parallels. This is the only software on my machine I paid for (go open source and freeware!). So I put in the CD I got from Parallels, and it contains 4 different disk images. All are different builds. Here are my concerns: Why the different images? Will I need a serial number? If so, where is that?