Removing dual boot after failed install

I recently tried to re-install XP Pro on a system I was having problems with…of course, the new install failed (I forget the details) and left me with a blue screen of death when I tried to re-boot.
Soooo…I press F8 at boot-up for a boot menu and now both the original install and the new setup appear on the menu. How do I simply boot into the old install (which at least still boots) without having to go through the F8 gymnastics and/or delete artifacts of the failed install?

Thanks