Common mistakes mounting socket A heatsinks include;
If there is a recessed lip on the bottom of the heatsink (Taisol is one) it's designed to fit over the lip on the socket. Don't mount it the other way!
Not removing plastic tape. The tape protects the underlying thermal compound while in transit and should be removed before attaching to the processor.
The white plastic mounting clips on the motherboard point down then recess behind them (towards the mounting platform). If the heatsink clips are left on the point, rather than being tucked up in the recessed part, you have no chance of mounting the heatsink properly.
I see this stuff done every day and have seen so many fried T-Birds/Durons I now usually mount the cpu and heatsink in the motherboard for Socket A newbies when they buy them.