You will need the CD itself, though if the original is damaged in any way a copy of the CD should be OK but to be on the safe side you should be given the original though damaged CD as well.
The most important requirement is the genuine "Product key" this should be on a Microsoft sticker and not something typed or hand written. The copy of the program should have been removed from the sellers PC and be eligible for activation. If not sure check the number with Microsoft, they will confirm.
The surplus to requirement copy from a training establishment will not be legal for home use as it will have been issued under a different licence code/agreement. j.