XPS 210 Fan usage (noisy)

Hello,

Ive had my very trusty XPS 210 for a number of years now, have never used it for gaming (yes, I know) but was purchased because I do lots of CAD work & at the time that was the best way to get a decent enough macine to run it.

Now however, I have noticed that the fan seems to be having a mind of its own. To the extent it runns so loudly its like a jet engine is taking off in my office!

Thinking this could be due to it trying to do too much have had a good clear out of softwares no longer needed, cleaned out all the internet clutter etc & made sure its been defragging as often as possible. It helped a bit as it now doesnt seem to do it 'quite' so often but still is doing this fan running into overtime & sounds like a space shuttle is taking off.

Should I be looking at replacing the fan?

Is there a software I could buy that helps with it keeping the PC cool by managing it?

Is it a common fault with this PC?

I did upgrade from windows XP to Windows 7 last year & its been doing it on both OS's

If anyone could help guide me in the right direction with this I would really appreciate it!

Heidi