I just replaced the motherboard in my T40 2373 with a reballed one from an R51 1829. I also upgraded the CPU from a 1.5 to a 1.8 Dothan.

I'm worried about the amount of thermal paste I applied to the new CPU. Having never done it before, I hope I put enough, but not too much, on the chip. The directions and pictures on the Arctic Silver Web site were excellent, but I'm just paranoid. This machine and I have been through many years together, and we need to get through a few more.

I installed the TPFanControl utility to monitor the CPU temperature and fan speed.

For general purpose use (no gaming or anything particularly CPU or graphics intensive), what is a nice, comfy temperature for this CPU? If the CPU is staying at a reasonable target temperature, then I hope that means I put enough paste on it.

I guess you should see the temps in the mid-40s C when idling, and sky is the limit when you push the machine hard.

Thanks for that observation! Do you think the break in period of the Arctic Silver thermal paste will even be noticeable? When I read their directions, I got the feeling that one might see changes in multiple core CPUs with attached heat sinks, not these little Pentium M chips with the small mirror finish part that comes into contact with the copper fan housing to dissipate heat.

Rule of the thumb is to use a drop that is roughly the size of the grain of rice, and spread it evenly with a credit card over the area on the CPU.

Break-in time is 24-48 hours from what I recollect.

Proper seating of the heatsink against the CPU is as important as the paste itself, and if you've done anything wrong in either of these areas, you'll soon find out. Hopefully not...

Gulp. How would I know if I hadn't properly seated the heat sink (fan assembly)? Excessive heat from the CPU?

Thanks for your patience with my lightweight hardware knowledge.

Well, if you see the CPU at 85 degrees C after 5 minutes of idling, there's something wrong with that picture, but I doubt that you'll have issues...just observe the machine's behaviour and don't stress over it...