Can anyone point me to what is causing this?

(Reposted because the other answer was unhelpful)
Hi, I have a Dell e321, XP Media Ed 2005, and that's about all I know about its specs. I've had it since 2006, it runs decently (as best as can be expected for an older computer that hasn't had any upgrades) up until the last week.
It started with my monitor not "waking up" after I woke the computer itself up from hibernate or standby. I'd just manually restart the computer and it would come back.
Now this morning, I tried to turn it back on, and the computer itself turns on, all lights green, but it will not communicate with the monitor at all. I know it's not the monitor, I have two different monitors and neither will communicate with the computer.
It seems to me - not being a tech person at all, just going by common sense and process of elimination - that it must be a problem with my graphics card. I believe it's the original one that came with the computer, so it's probably due for replacement anyway. But I searched online, and others who have described my same problem have been suggested that it is the motherboard or the PSU. It seems to me that the computer wouldn't make all its normal startup and "turning on" noise if it was the power supply or the motherboard, but as I said, I'm no tech person, and I can't tell if it is the motherboard because I can't view anything on my monitor.
Any direction would be much appreciated. I don't have much money to spend and I can't replace the computer itself, so I'm avoiding throwing extra money at the Geek Squad if I can find out the problem myself.
Thank you!