The 'square of something on the bottom of the heatsink' pinky in colour is a cooling pad. These are not usually any good. Generally heatsinks that come with that stuff on them are not to be used on highend systems.
Get rid of that stuff by removing as much as you can with an impliment that will not scratch the base of the heatsink and then clean it thouroughly with Isopropyl alcohol. Then get some heatsink compound (several to choose from), I usually use Artic Silver 'ceramique' as it is non conductive and apply a thin layer over the cpu core. Then put the heatsink back on top.
For better cooling you should really buy a heatsink that is all copper with at least an 80mm fan. A high quality heatsink will not have any paste whatsoever on the base.
Asus A8V Deluxe Rev2, Bios 1014.008, A64 4000+ San Diego @2.88Ghz (firstname.lastname@example.org), XP-90 w/ Enermax 92mm, BFG 6800GT OC 370x1000, Creative Audigy, Corsair XMS TwinX 2048-3200C2PT (2.5-3-3-6 1T@2.7v), Seagate 500GB & 250GB SATA (Promise IDE), OCZ PowerStream 520w, Lian Li PC7 Plus II (3x120mm fans)
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