I bought a package of an old but never-used motherboard, CPU, and RAM that fit my needs. (And what a bargain, for only US$79. If they work.) The photos indicate that the CPU and fan have been mounted. (Unless I find that those are mere stock photos. Going to find out from the seller.) It just occurred to me that if the CPU and fan are actually mounted, the thermal paste may be dried up and needing replacement if someone mounted them years ago (must find that out as well). The board model is Asus M4A785TD-M EVO and it's about fifteen years old according to my research. I'd better make sure I have some paste.

While applying new good quality thermal paste is never a bad idea, and can head off any possible thermal issues before they even begin, it shouldn't hurt to power up long enough to enter BIOS Setup and look for a tab/entry for something like "Hardware Info" where you probably can see temperature sensor readouts. This should also verify that fans are working properly or show the option to reset them..

I am rather a fanatic about electronics temps so I like to see temps well below ~45C (lower is better) but even 15 year old CPUs have no problem running even 35C higher but that would bring me to action though it isn't altogether uncommon for some users especially on poorly cooled laptops.

If you have the oem clipon cooler from amd . The plastic brackets that are screwed to the mobo that they clip on to can get brittle and crack once the plastic loses the volatiles. Then the cooler can pop off the cpu. The mobo bios will have an overheating auto shut down threshold. Please check bios to make sure it is enabled and on sensible temperature. I had this sceneario happen to me personally twice. If one day your system powers down by itself for no reason check your ancient amd cooler mounting bracket first.

I'd power up first and see what you have (ie. Does it work?) .... Then modify if you still think you need to.

Personally, I wouldn't bother until you intend to commission it. If it's just lying about unused, why put on new paste?

My guess is the paste never goes bad unless it leaks out at 200 degrees.