hallo!
I'll try explain to you what i did..
I tried overclocking my system
( My system :-pentium III 733 with FSB 133
-motherboard MSI..(i'm sorry i don't remember anything else about it!)
- RAM 512 in 133.
i think these are enough).
I changed the settings of the BIOS and these are the changes that I made :
from 130hz to 150hz
voltage from 1.65 to 1.75
sddram cycle from 3 to 2.
When i startup my computer i didn't hear any sound (you know the usual beep) that means the systerm won't POST, my monitor it does not correspond (displays "NOT SIGNAL") and the four lights on the motherboard they continue being red. Ah! the fan of the processor works!! The processor i don't know an it works but the fan works! :)
If you have any idea for what it should I make him I would appreciate particularly inform me!!
(I apologize for my terrible english!)

sounds like you've over clocked it too much and accidentally cooked the system.

best to take it to a techie pro

Reset the BIOS by either switching the jumper on the motherboard or removing the CMOS battery for about 5 minutes. Once the BIOS is cleared you should be able to boot with the default settings. You may want to try smaller steps in the future if you want to overclock the system and try changing just one thing at a time.

Agreed. You only need reset CMOS as BuggZ has said, to allow the system to boot with default and autodetect settings. It's a simple procedure and a common task faced by overclockers who've pushed settings too far to allow the system to boot :D