Inspiron 530 Memory / Video issues

I was asked to look at a friend's computer.  I was told that when they tried to turn the computer on, it would beep continuously.  When i get the tower and connect everything, it beeped 4 times with a blank screen.  I went thru removing and reinstalling the memory modules 1 by 1 (there are 2 - 1gb modules & 2 - 2gb modules that came from Dell)...the 2 - 1gb modules are installed in slots 1 & 2...any memory module installed in 3 or 4 would lead to 2 beeps on startup...and still no video...i tried to connect to an Pci-e video card to see if that was the problem, but nothing..so i'm thinking the power supply doesn't provide enough power for the card...so i still have 4gb of memory not installed and no video at all...the monitor does not come out of standby mode at all...what can i check/do?