Having spent all morning solving this problem, I thought I'd share the solution in case it helps someone else out there...

Inspiron 530 and 545 PCs won't boot Ubuntu 13.04 live DVD. Boot error message shows. DVD works fine on other PCs

Attempted Solution:
Use USB image. USB stick works on other PCs, not on the Dells

Actual Solution:
1) Burn plop boatloader onto a CD http://www.plop.at/en/bootmanager/index.html
2) Make USB image of 13.04
3) Run plop from CD
4) Choose USB and boot into 13.04

Hope this helps!