If you are stopped trying to install service pack 5 it's about clearing out some temp files in the Crogram\omega directory somewhere, just clear all of them out and it will load SP5. I never had trouble installing that software except at the SP5 point.
Delete the complete Omega Research diectory.
If you have Service Pack 5 you can directly install from that disc because it is a full version. So only install SP5, nothing else.