About this time I've had it, and I call Adobe tech support back and explain my problem. Now, if theres a silver lining in this story at all it has to be that Adobe's tech support staff are very cool, very helpful, and actually have answers (you can tell they never worked for Dell). "Jeff" at Adobe informs me that I should uninstall CS3 AND CS2 and try again.
He also fills me in that the CS3 cleanup script has two more levels of cleanup (levels 3 and 4) that don't appear in the options. I assume this is because of what its about to do. Level 3 will remove/cleanup not just CS3 remnants left on your system after uninstall, but those left by the CS2 uninstall as well. Level for will do this for ALL Adobe products. So he suggested I try removing CS2 and CS3 first, clean with level 3 (run it as many times as needed until no more files are found). Then try installing CS3 again. If that doesn't work then uninstall all Adobe products, clean with level 4, and try the reinstall.
http://www.cruciallimit.com/blog/74/adobe-cs3-install-horror-round-2/