What do you mean by "not boot"? Will it POST (the stuff you see on screen before the os loads)? If so, then it's a software probelms and I suggest getting some config that works, backing everythign up, and reformatting
If it does not post, then unplug all but the essentials from your computer (keep ram, HD, vid card, ect) and see if it boots them. If it doesn't, Isadly don't know enough to help, other than to say RAM the cards ASAP and try the new ones they send you.
Also, if any of those cards have a seperate power plug on them, it would be a good idea to make that work.
EDIT: was about to say that...
AGP won\'t fit in PCI-E... unless you use a really good hammer. ~Trotter