Your problem is no display, check your monitor screen, you can plug it out in vga port and insert it again and power up computer if it solve. Now if not you need to check whether during power up there are any beep codes, if no and yes you heard beep codes but no display you need to check your video card and memory. Because this two parts are commonly cause of no display. Clean it if necessary using pencil eraser clean the contact pins the one that have color gold.