why did my CPU get fried?

[DarkManX]

my computer is running an asus A7N8X Deluxe with an XP1800+ cpu, i took it out to test another cpu (AMD t-bird 1200MHZ) it didnt post like i suspected because i thought the cpu was dead, i took it out and put in my 1800+ and suddenly smelled something burning took the cpu out and under the cpu in the middle it looks all burnt so it looks like the core got fried, why would this happen?

 

[Mik3y]

did u use thermal paste? was the hsf fan on correctly?

 

[Matthias99]

Bad heatsink mounting? Your other bad CPU fried your MB (which then fried your good CPU)? You somehow broke a pin and reinstalled your CPU backwards? ESD fried some of the diodes on your 1800+, which caused it to short out when you plugged it back in? Little gremlins?

 

[MDE]

I'd blame the gremlins.