I have used Microsoft Fix-It tools to generally good effect on my In-laws XP computer. They are the kinds of people that give the Geek Squad nightmares even as they run the credit card. Beautiful people whom I love and respect like my own kin, but victim to every "Your computer has been hacked with viruses!!!11!1" pop-up known to man.
The last time, they were a victim of ransom-ware, with most of My Documents locked behind admin permissions (IIRC) and the Start menu gutted (was switched to Classic start menu, with a few empty folders and app shortcuts remaining, nothing in the Settings sub-menu). Microsoft Fix-It actually fixed ~80% of the errors, with the rest being done by me manually (I had to re-enable the full start menu, uninstall the rogue toolbar and malware, etc.), so now their computer is hovering around 95% OK (fingers crossed), the rest can only be fixed by a complete re-install.
I decided to trust it because it IS put out by Microsoft themselves, who should know how their own systems work, and not a third party who may or may not have read the uninstall API correctly. I'd say back up what you can, say a prayer if you're so inclined and pull the trigger. Your only other options are leaving the uninstallers as they are (safe), or trusting a third-party app with a good reputation (potentially unsafe).