You'll need new thermal interface material (TIM), e.g., Arctic Silver 5 (AS5). Assuming it is a Intel pentium cpu or newer:
-- Turn the pin-locks a 1/4 turn counter-clockwise so the locking pins unlock.
-- Then lift the heatsink from the cpu and board, do this carefully on the stock heatsink because the TIM may be holding it to the cpu.
-- After you remove the current heatsink, you can clean the old TIM from the cpu with a lint-free cloth or coffee filter paper.
-- After you get most of the gunk off, you can use a fresh filter paper and a little rubbing alcohol to remove the rest of the old TIM.
-- Now you can apply the new TIM to the CPU (follow the manufacturer's directions as to the thickness and coverage). For AS5, you put a very small amount on the cpu, and use a clean filter paper to spread it over the cpu, leaving a haze (like car polish), then put a small dab (about the size of a grain of uncooked rice) in the center of the cpu. Then you install the new heatsink (if you use AS5, you'll need to follow the same steps to clean the heastsink, but don't add a dab of AS5 to the new heatsink base before you install it).
-- Follow the manufacturer's instructions for installing your new heatsink.
another high alcohol solution is in your other halfs drawers,
no, not the american version of drawers
nail varnish remover works fine,just remember to remove any dried residue before applying new paste,
watch a few vids on youtube for paste amounts/application, you seriously need a tiny amount, I mean spicegirl IQ tiny