I know it's annoying to reinstall but I find this the best approach in general. Also, having regular images of your OS is useful. Definitely worth the effort to make one once you've finished setting up your system and have everything in place and running.
I only ever had similar issues (doesn't install/some shields not running/takes ages to load/crashes/...) on old systems installed years ago. Never ever on a clean fresh system. Getting it to work is a great excercise if you are masochistic and like to dig into things, but... extremely ineffective considering the time spent on it. So, the only positive is the learning experience perhaps. Note that NONE of the systems I didn't reinstall was actually infected. All problems caused by previous security software incompletely uninstalled, leaving drivers, services, registry crap and whatnot there.
If I encounter an infected machine, I format it. While people dislike it at the beginning, since usually the computer comes to me with tons of junky apps installed, plus a bunch of stolen games etc., they in most cases are very happy after getting their computer back in clean, sane state when it runs and doesn't take half an hour to just boot.
