System is dead, no cursor, no beeps, no fan

There are four possibilities:* Power cord failure- Plug in or replace power cord. Power cords can fail even if they dont show any external symptoms
* Power supply failure- In this case replace the SMPS. If u r going to mend it urself, u may replace it with an SMPS that u kno is in good working condition, otherwise get the help of the manufacturer.
* Motherboard failure- Replace motherboard. Use a motherboard that u kno is in good working condition.
* Memory failure- First take the RAM from the RAM slot and try cleaning the slot and replacing the RAM back into its position. IF it fails, replace the RAM with a new one in good condition. While replacing the RAM, keep in ind that you replace it with another one which is compatible with your system configuration, i.e, if it has the same bus speed and memory etc like the faulty one. If u have multiple slots remove all the RAM except the one in slot number 1 ( to be precise , bank 1) and try to reboot the system. If it fails, retest with the other RAM.