ok here do this take the heat sink off clean the heat sink with a #2 sand paper now get your self some heat sink glue you dont need to but it helps after cleaning make shore u clean the fan becouse if fan is dirty it will over heat p4's run about 120 to 130 f thats ok hdd should not get more then 115f now here is a good ideal get your self a tornado fan it works very good keeps your temp down email me SNIP if you need any more help i working on web hosting and pcrair and programming been doing it for years so have fun hope it works good luck

Far out mate. A little punctuation would go down well .
To the OP. First off, no need to be taking off the heat sink just yet.
Take the side cover off the case and have a look at the fins on the heat sink. If it is full of dust, clean it out completely using a small artist's brush, or some compressed air.
If it is not full of dust, check that the fan is turning when you start the pc up.
If you still have problems, post back.

but see i know it may be a lot of work but this takes care of most problem yes you can do that but most people that know how to work on computer will have that stuff clean easy over look so doing you way is good to but most of the time it dont last long this way i giving you a long last time befor you got to clean again

There is absolutely NO need to take sandpaper to the heatsink, unless it is not flat. ie; convex or concave.
If one ever needs to, then clean the surface with Isopropyl Alcohol.
That will remove all the original TIM (thermal interface material), so that one can apply it new.