Don't you need to force/solder the pins of the the optical drive to "master" to get it to boot? The drive you installed is probably set to cable select. Might also be the reason why the HD doesn't detect. Also check if there are any jumpers on the HD itself - unlikely though.

If you have a dremel with cutting wheel, you can cut a notch out of the bung screw, or just drill it out - with a slightly smaller bit it will not damage the heatshield's thread. Then, it might just be some dodgy RAM, of the CPU daughtercard not pushed in properly - with luck!

JB