Half-installed game wont finish install or uninstall

[Pip Boy]

I tried to install Assassin's Creed 2, and just like every other game that uses Direct X, the installation froze at the part where it tried to update my Direct X. This unfortunately left me with no choice but to end the installation early, and now there is a partial installation of the game on my computer. If I open the disk's autorun and hit Install, it instead attempts to uninstall the game, informs me it has successfully uninstalled the game, but then when I try to install it again, it does the same thing, trying to uninstall it.

I've been fighting with this stupid thing for a couple of hours now, and usually my computer problems dont solve themselves until right after I post them, probably just to spite me for having asked for help.

Anybody know how to fix this?

[EVILNess]

Go into your c dive and delete the files manually. Then restart your computer for good measure.

[Pip Boy]

I deleted all the program files, but Im still having the partial install problem. Unfortunately this probably means that the files that would need to be changed are those cthulian .dll files, and I don't think I should just go pokin around in my registry without some kind of walkthrough for it.

[EVILNess]

Try running CCleaner. It might be able to clean up those unused registry bits that are causing your problem.

[Pip Boy]

Ran CCleaner, and still running into the same problem. I can't run the installer, and the uninstaller leaves it thinking its still installed.

EDIT: Nevermind, had it delete the game from my list of installed programs without running the game's uninstaller. Now the install is running again. Hope it doesn't hit the same problem.