Computer posts, beeps, then restarts.

Hello, skip to the end for my questions,

I recently was given a used Intel motherboard with a stock cooled Intel Celeron 3.06Ghz CPU, and 1.5GB DDR400 Ram.

I attached this to my IDE HDD in my other computer which is running XP SP3. All of this inside a stock Antec 300.

My problem is that when I start the computer, it posts, I can see it on the monitor, but after it does the memory and I/O checks, instead of starting windows, the screen goes blank, it beeps and then restarts itself.

After it restarted I went to setup and It said my processor was running at around 85C, of course I realized that this is way too hot, so I shut my computer off and checked the processor by removing the heat sink. I found that there are remnants of thermal compound on it, but not nearly enough.

My questions are these,
Does having no thermal paste account for the huge temperature increase?
Will an overheating CPU restart my computer after it posts?
Would reapplying new thermal compound fix my problem?


Thanks in advance for any and all help!