I'm stuck on the gray screen on start up

If removing the troubled drive allows you to boot to the Snow leopard DVD, just follow Kappy's "Downgrade Lion to Snow Leopard" procedure above.

If you have a working printer, you could print that procedure or the whole thread.

Installer DVD, Safe Mode, and the Apple Hardware Test all use very simple graphics modes. One of those may allow you to learn something.

The gray Apple comes from boot files on a drive (probably BootX). When the gear stops spinning, it switches the graphics card to "automatic", interrupt-driven mode. A failure at that point implicates the graphics card.

Safe Mode does one pass of "Repair Disk" then loads a minimal set of extensions. It is intended as a way to recover from installing something that did not go well, so it provides full access to System preferences and Finder features to re-arrange files as needed. It also uses very simple default graphics modes so that you can use it to recover from setting the screen resolution out-of-range.

For the benefit of folks looking into this sort of problem, could you share your decision-making process and final reolution with the forum?

The next guy with a similar problem will thank you.