There are so many tools out there that it's easy to get confused. So please recommend me some PC Optimization software (freeware, shareware, etc.) that you've used and works well across all Windows versions — Win 98 / Win 2000 / Win Me / Win XP & Windows Vista.

What do you suggest

There are so many registry cleaners nowadays. Maybe somebody knows what is the most effective.

registry cleaner??

My computer has been super slow lately and it's getting really frustrating. I've been told that I need to install a registry cleaner. Would that really help? Where can I download a FREE registry cleaner from the net that also works effectively?