If you're looking for an OSX86 distribution to put together a hackintosh, especially if you're doing it (obviously for educational purposes only) on a Dell Optiplex 745, I would recommend the iPC 10.5.6 distribution (PPF 5) which you might find on a place that sounds a bit like the Birate Pay. For the Optiplex 745 I would recommend using the Azalia sound drivers and the Intel ICH* chipset/ATA drivers when installing. I would then recommend searching for NATITX1300 on google and downloading and installing the drivers you would find there, ignoring any errors reported during installation. To avoid kernel panics when mounting Disk Image (dmg) files, I would look at this link.
Not that I have actually done any of the above, of course.