com.apple.dock.plist does not exist.
Click on the Face Icon in the Dock to get a file window or
Click on the Desktop and when it says "Finder" up in the left corner Go File > New Window
Once you got that on the left is "Places" and under that is the name of your "user" account click that
In the window on the right should be a list of folders, one of those folder is called Library
DoubleClick on the Library folder and scroll down until you see the Preferences folder
Doubleclick on that and inside there is the
file, click and drag it to the Trash can and from the Finder menu > Empty Trash and click OK
Now reboot your machine.
What is an internal boot drive and where is it?
It's the internal storage where everything you have on the comptuer is stored.
When you hold c and boot off the installer disk, a couple of screens in there will be a menu option for the program called Disk Utility. You launch that and then select your drive on the left and click "Erase" and you chose a format, the defualt format is HFS+ Journaled which is what you want.
When you click OK, the disk is formatted and all data is eased.
When that's done you quit Disk Utility from the menu and you have a option to install OS X , you do that next.
Once that's all done you reboot the comptuer with TimeMachine hooked up and go through the setup like when you first got the computer.
Then it will ask you to restore from TimeMachine and you say Yes!
If you think you can't do this, take everything, your computer, the disk and the TimeMachine drive to someone who can or the Apple Store.