What compound is used INSIDE a processor?

You had the metal heat spreader peel off the top of one of the processors? Im not sure what they use to stick them on but it would need to be very thermally conductive, i wouldnt use glue or anything, they may have used a thermal paste on the main part of it and some adhesive around the edge.

Yes, hunter315. I could not remember what the processors top or lid was called - it is the heat spreader. Yep. It has come off the processor (the RSX one) revealing the actual processor in the centre on the diagonal, and 4 DRAM type chips at each corner. The normal thermal compound I use to stick heat syncs on won't "stick" so I guess it is some kind of thermal compound which has adhesive properties also. Many thanks.

A permanent adhesive such as Arctic Alumina Thermal Adhesive or Arctic Silver Thermal Adhesive would do. Great care should be used in applying these as the cured adhesive is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths.