You an try a couple of things: (in the given order)
- Reseat your RAM modules, if no joy test one by one, cycling through the available slots, or borrow known good modules to try.
***Keep in mind to disconnect the power cord and wait at least 30 seconds before you unplug or plugin your RAM and/or plugin cards!!!***
- Replace the RTC battery on the motherbard. Some MoBos don't boot if that battery is low
- Borrow a PSU if you don't have a spare and try if that helps
- Last thing - disconnect everything except RAM, monitor and keyboard from the MoBo and try if you get something on the screen. Could be plugin cards or drives (HDD,DVD,FDD?) playing up.