ok i had to add a new power supply cause my pc wouldnt boot up.. now it boots up but i have no INFO being sent to my monitor.. monitor does work and all the cables work cause i tested with another tower.. some say video card. others say motherboard.. i have a compaq presario..You havent SAID too much.  When did this happen and why did you think it was the power supply?  It boots up you say ...how many beeps?  You said it wasnt the monitor but......have you tried another monitor just to be sure?  When you tried the monitor on another tower it worked fine?See below.First... I hope you removed the old power supply... Lol   anyway... It sounds LIKE a problem with the video card and the mother board... Make sure that the video card is in its slot nice and tight (Do not be afraid to push it in a little bit... NOT WITH A HAMMER THOUGH! I LEARNT THAT THE HARD WAY!!!)... If it still doesnt work remove the VIDEOCARD and get yourself a can of SPRAY air... And spray inside the slot... Then put the card back in... If it still does not work call GEEK SQUAD

GEEK SQUAD RULES, GEEK SQUAD RULES!