Disc 1 is definitely bootable. If it doesn't boot, e.g. no bootable
media found error, then it's not burnt properly.
Reburn another Disc 1 will do you well. It is recommended to do md5sum
check on all the iso images after download. big files get corrupted
easily, and without check it's usually a bunch of RPMs inaccessible.
Sorry it bumped you there, where it shouldn't. booting off CD is not
where one should get stuck at ;)