I recently build a PC at my own very first time. Surprisingly, it was 100% Ok and I used it for around a month. Later I sold my PSU and RAM to a guy as I have an other branded PC for my own use. Now I again bought used RAM of same specs i.e. DDR2 800MHz and a PSU of Coolermaster 650 watts and installed them in. However, there comes no signal on my monitor even standby orange light doesn't go green for a second. Similarly there is no power / light on my keyboard and mouse while CPU fan and two other case fans are spinning and CPU led is flashing properly. There is no beep sound whatsoever until I remove the RAM. The tower looks working but no output. I checked my monitor, hard drive, graphic card and RAM on other system and they all are working fine. I arranged an other PSU of 450 watt but no success. Even I replaced my CPU but in vain. While motherboard supplying power to all fans, its system light on board is flashing, and when I remove the RAM it properly gives the beep of no RAM but still nothing on monitor, keyboard and mouse. I tried different dimms but no luck. System consists of following components: 1. Motherboard Asus P5QL Pro 2. CPU C2D E7500 3. RAM Kingston 2GB 4. PSU Coolermaster 650 and Absolute 450 watt 5. Hard Disk Seagate 500gb 6. Graphic Card MSI NX7900 256 MB 7. Casing ATX CoolerMaster I think my mobo is OK as all fans are spinning, board and led lights are fine and it beeps when there is no RAM. Please help me out as variety of options I so far applied could bring no fruitful result.