Don't use automated or software-based overclocking tools for the CPU, learn to do it manually via the BIOS. You'll have greater control over the settings you need and can diagnose issues that arise.
If you're new to overclocking, start here; http://www.tomshardware.co.uk/forum/272214-29-wolfram-beginner-guide-overclocking.
Overclocking is perfectly safe if you know what you're doing.