If you only have one PC in the house, then you should not be tweaking and clocking IMHO
EDIT: That sounded negative... what I mean is... if you have only one PC in the house you must have a means of data recovery for tweaking, drivers and OS install disk handy, in case something goes wrong (a disk image will guarantee your down time is minimal)
For overclocking, especially playing around with alternate cooling setups, one should really have a second PC handy incase something goes wrong.