dell inspiron 2200 no display, fans ok, hdd ok

It's old enough to have failed (2005 laptop) but did you replace the CMOS battery and give it another reset?
I've noted the routine at my sticky in another forum. Link follows.
http://www.cnet.com/forums/post/30c241c5-dd8b-4d73-b08d-c6e15897fe5f/

Many laptops have a reset feature. Some don't but as not all machines have it, here's something to try when a laptop won't start. Remember this is generic, doesn't apply to all machines but when faced with a non-starter dead laptop, why not try this?

Ready?

1. Remove all connections to the laptop. (USB, power, etc.)
2. Remove the battery.
3. Press and hold the power on button for 1 full minute.
   -> Explainer. Yes, many machines only require 10 or 15 seconds but this reset instruction is generic and I've found people hold the button for 9 or 14 seconds so let's write the full minute.
4. Let go of the power on button.
5. Slip in the battery pack.
6. Plug in the power to the laptop and to the wall.
7. Do not plug in any other devices.

Try the power on button!

Thanks for the reply,
here is what i did

i removed a coin cell battery and a removable RAM (it had got a built in non-removable RAM too). Then i hold power button for 52 secs, then rebooted again.
Power led is lit, fan is spinning capslock numlock and scroll lock flash once for about 1.5 sec then the leds goes off, power led remain lit, with the fan spinning at constant speed even for an hour. But internal and external monitors (display) remain black, no any sign of picture color or power (on internal display)

Tested monitor on another vga computer, works pretty fine. But when hooked on my dell it says no signal.

somebody told me to press D button or fn button while powering it, and here is what i got

"D" + power = no changes, pc comes up but no display, no any visual, real blank (no signal on monitor). tried Fn + f8 which is display switch, but no effect.

"fn" + Power = power led on, fan on (like previously) but now numlock s off, also scroll lock remain lit and capslock is flashing continously for even 30 minutes without pattern (it goes off only after powering off the machine)

It is my grandpa lovely pc and i would real like to bring it to life, as buying a new one will NEVER make me feel worth like if i would cure this one,

thanks again in advance

In this case I'd replace the motherboard. It holds almost all the parts that produce the display and make it work.