Viewing videos does not require much horsepower - in fact, many motherboards with on-board graphics make excellent
home theater computers (HTPCs) used for PVRs and watching DVDs and BluRay disks. Many HTPC enthusiasts and audiophiles under
clock their systems to reduce heat for "silent running" - totally passive (no fans) cooling and still have error free HD display in full surround sound.
Generally, if you need to ask, you shouldnt overclock... its too easy to damage or destroy your computer...
I agree 100% - and it should be noted that any damage will not be covered under any warranty.