First, CPU time of 142 years total is correct. Each day adds a number of years CPU time. Just add up all the hours for all the computers runnin simultaneously.

Last, the Forum suddenly signed everybody out. I had to sign back in. ???

In the middle, CPU usage of 100 % is reasonable for a big desktop with lots of air blowing through it as long as it is not overclocked with a tremendous graphics card. However, laptops are compromise machines (think pistol as compared with rifle) so this can be a genuine concern. For a Dell Dimension, the only problem should be with fan wear, assuming the room is cool and nothing is blocking the air.

I see so if its 1 hour of 1000 CPU's, that amounts to total 1000 hours CPU time. And this disregards how fast the CPU was, right? If you took the speeds into account, it would become much more complicated (like a weighted average system), e.g.:
10 hours of 500 Mhz (may be equal) = 1 hour of 3Ghz P4 [just an example]
So I take its not this kind weighted average system because you'd have to shift everything when new CPU's came out and blah -complicated.

Anyway I tried installing many CPU/MB temperature monitoring softwares and now I tried your Motherboard Monitor which seemed the best software. It said I have no 'Main sensor' and so that wont work.

I did a crazy thing, I had this extra $2.99 12v fan so I hooked it up in the CPU and now there's 2 fans cooling my CPU. I checked the temperatures with my fingers and the extra fan did make a difference. It tries to push the other older fan to go faster. Its a little more noise (fast whirring sound), but anyway atleast its running cooler. I'll keep it like this until something else happens. I checked from the Intel site, my CPU seems to be consuming 80~100 watts somewhere in that range and higher CPU usage probably adds only 20 more watts, however more wattage from the input side(110v) would be requried since no system is 100% efficient. I'll wait to get an ammeter to get an accurate result.
and I did check the die temperature at 100% cpu usage -that thing is hot to touch! With another fan, it cooled down significantly though I wish my MB would work with the monitoring software so I can get accurate readings.

I started my task today and its already 30%. I heard it takes usually a week to complete the task, so maybe my CPU did real good eh? Or did I misunderstand?

And this project just started on 9/20, 2 months ago ?(looking at the usage graphs ). That means the graph is going to climb up very fast as new users are being added.

I see.
There's a huge increase in the swap file when I run the program - It increases by 300 MB and my total swap is now 570MB. Is it necessary to use this much swap space? I was hoping to buy 512MB RAM to have my total as 768MB but with if I continue to use the program, the swap will still be tight.

First off, weighing CPU power vs time between the masses of different processors out there would be difficult and a pretty intensive statistic to generate and wouldn't be so hugely relevent. They do the next best thing by doing a comparison between time vs results returned.

Dells do have sensors onboard, but usually they've been disabled via the BIOS or the BIOS hasn't been updated to enable temperatures to be monitored during windows operation.

As for your swap file increasing, this is normal under regular windows operation. You just don't regularly notice this as when you're running CPU intensive programs (games etc) you're not looking at your swap file at the same time. It's just that this program tends to run in the background whilst you go about doing whatever you do on your computer and thus you can actually see the windows managed swap file increasing.
Also, 570mb isn't that big at all for a windows swap file, you'll find it will sometimes increase into several gigibytes when intensive programs such as video editing and even games. The swap file is stored on your harddrive and not in RAM, you should have at LEAST that amount of space free just to run Windows XP properly.

Also when buying RAMM, you're using an Intel HT which 'typically' has a dual memory interface provided that your motherboard chipset supports it. But then Dell is pretty cheap with it's motherboards, check your motherboard manual to confirm it has this ability. So it tends to be better to swap out both DIMM sticks with identical memory for noticibly better performance. In other words, sell your current 256meg RAMM and buy 2x 512meg RAMMs.