usually not, mfr do checks on the pc to see if that is the correct brand...ie your installing xp from compaq on a dell box, that's most likely gonna crash...plus the drivers that are included could wreek havoc on your machine.
I wouldn't do it.
Depends, but usually yes. This is how DELL and other PC manufacturers usually do things, for the obvious reasons.
Anyway, if you've got the authentication card and EULA page, you should be able to read what the license allows you to do and what it doesn't allow you to do. (That's why they give it. )
Anyway, given the nature of most name-brand PC's, if the CD came OEM with the box, chances are it's not transferable.
Technically, if you've just got the CD and nothing else...you don't legally have the software (which also means it probably won't authenticate after installation...if it installs).