I got a Dell d600 but i cannot get into cmos setup

Have you contacted Dell tech support?

Make sure your computer is shutdown while doing this. Remove the battery. Press the power button after removing the battery to discharge any stored volts. Flip the computer so the battery side is facing you. Unscrew and remove panels until you see a watch battery. It will look like this

Remove this battery. Wait 60 seconds. Replace battery. Replace panels and screw back together. Replace battery, power on. This should have reset your BIOS/CMOS settings. Why does this work? Because this battery is what keeps the minimum amount of voltage running through your CMOS/BIOS chip to keep the settings intact. Removal of this battery restores factory defaults.

Oh, by doing this you will have more than likely have to reset the BIOS time and date to current time and date as well.