not tryin to be a jerk...but that is wrong info....
thermal paste goes between the top of the processor,and the cpu fan heatsink....
its what keeps the heatsink and the cpu core from having metal to metal contact.
you would apply a very thin layer directly to the core of the processor and then install the heatsink/fan.
if your board is comming with a new processor and fan and is assembled to the board when you get it you will not need any thermal paste.
having capacitor issues as you explaind happen...
ive seen motherboards last 6 months ive seen them last 6 years.
its just like anything else electronic it can fail at anytime for no reason
alot of it could be too,is that dell is well known for not using the best of components in there machines.
Dan