Instead of booting to "a different drive", boot to the Recovery HD partition of this same drive.
It isn't useful to try to repair the file system of the whole disk. A disk could have more than one type of file system. You repair the file system of a partition. A partition is one file system.
The upgrade DVD is not the original full OS install DVD, so it is like a retail disc, has dual-architecture, is not computer-specific.
If you had a grey restore DVD that is labeled with the computer series it was meant to restore, that cannot be used for another computer series.
There is no stop sign associated with Mac startup. You see a stop sign at a road intersection. Could you be seeing a prohibitory sign (as in "you are prohibited from continuing"; a circle, not a stop sign). If so, it means the bootx file was not found. Either the HDD has a corrupt file system...
Seems we lost the OP; got his answer and split.
dkennedy:
You took over in his place, it seems. I think you are not stating this correctly. You did not buy a "Leopard Mac Box Set" because their never has been a Leopard Mac Box Set. You bought a "Snow Leopard Mac Box Set".
The "Mac Box Set"...