Hi i just removed my heatsink fan, i'm just wondering if i need to get some more thermal grease (heat transfer compound) before i should put it back on, or will it be fine without any?
sorry for newbe question.. 
I'm going to assume by "heat sink fan" you mean you removed the entire heat sink, metal parts and all, completely off the processor, since there is no compound between the fan and the metal part of the heat sink.
What I do if I am caught without any thermal transfer compound and I am swapping out a heat sink (or a processor and keeping the old heat sink), I scrape off the old compound from the old heat sink with a razor blade and push the glob back onto the processor chip (in the center) and then attach the new heat sink. The excess will squeeze out around the processor chip, which is fine. As long as you keep the compound clean when you do this, it should work pretty good.
This trick is my last resort, though, and I only do this if I don't have my regular computer repair bag/tools with me. Otherwise, I always wipe down the processor with a paper towel and dab on a little fresh compound.
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