What is a normal temperature for a CPU and what sorts of things can I do to keep it cool? I have seen it go as high as 97 degrees C. Water boils at 100.

An avg of 65 or > is pretty bad, IMO. Even with the standard, stock air cooler it should only be around 40 - 50*c. That's also with a very high ambient temperature. BTW, 100*c is the threshold for most CPUs and BIOS before they'll auto emergency shutdown your PC to prevent meltdown (just some perspective).

I'd also recommend you take you PC tower out of and cabinets if it is because poor airflow can shorten its life by years.

What would be ideal temperature, IMO

Core # 0: 40 c (Max: 74)
Core # 1: 48 c (Max: 72)
Core # 2: 31 c (Max: 76)
Core # 3: 48 c (Max: 77)

That's if you've still got garbage hot ambient temps. You could use an air compressor to peel however many layers of dusts that's settled over the years.

The uneven temperature between the cores could be a result of poorly applied thermal paste. You might wanna look into that.

Lastly, I don't know too much about HWMonitor, some monitors allowed you to modify the fan speeds manually. As a result for most, you end up with a static fan speed which is only running fast enough to keep it cool during idle periods, your computer will instantly auto-shutdown to protect itself because of the lack of dynamic cooling. That is if you haven't turned that feature off, in which case your computer could very well cook to death.

NVIDIA GeForce 9500 GT

TMPIN0: 58 C
TMPIN0: 58 C

This could be higher because of the lack of airflow. In turn this will rise the temp of your CPU because of the rising case temp. Some of the older models of graphics card do produce more heat/per volt than modern fermi boards. Might be time to upgrade your graphics card (if you're using a laptop, nevermind).

Good luck, friend.