display turns into a screen of small shimmering colored patterns and the computer ceases to respond to any command.

Can you test this monitor on a different PC or a different monitor on this PC?

Are all fans working, including CPU fan and video card fan, assuming you have an add-in video card?

Assuming the monitor is ok, if you're using an add-in video card, you may want to remove it and connect the monitor to one of the on-board video ports (DVI and VGA) depending on what inputs your monitor accepts. The on-board video ports are disabled unless you remove the add-in card, so you just can't move the connector from add-in video card to on-board video.

Check the manual for instructions about working inside the PC and removing cards.

Thanks for the reply.

I recently replaced the cpu fan and the power supply fan a couple of years ago.

The video cards are not removable.

I connected the monitor to another computer and again after 20 minutes or so, the screen went blank white and the computer stopped responding. The machine does not turn off , it just stops responding to any commands. I have to hold the power button down for 10 seconds and then it turns off. I can push the button and the machine boots and starts normally but after a period of time it freezes up again.

Yes!

When I connect a different monitor to this pc, it is the same behavior.

Do you have any idea what could be the problem here? I was thinking of buying a new powersupply but I could buy a refurbished computer for the same $65.

I'm totally confused...!!  

You said you connected the monitor from the 4700c to a different PC and "after 20 minutes or so, the screen went blank white ".  That made me think the monitor is bad.

Now you're saying you connected the monitor from the other PC to the 4700c and "it is the same behavior".  

So how can that be? Either the problem goes with the monitor or it stays with the 4700c.  Unless you're just totally unlucky and there are problems with BOTH the 4700c and the monitor.  

Please explain...

Hello Ron.

Sorry. I meant that I connected the monitor for my new xps 8900 to the Dimension - as a test. After a couple of minutes or so, the new monitor conked out just like the other one. That seems to indicate that the computer is acting out.

What do you think.

brunetto

The video artifacts represent BAD Capacitors, Bad Power Supply and or BAD RAM.

Since you don't have an add-in video card, it could be the motherboard.

Any signs of over-heating? Are all fans clean and working? You might want to use some canned air to blow out all the dust bunnies, and reseat the RAM modules in their slots too.

Maybe even remove the heat sink, clean both surfaces and apply a new thin coat of fresh thermal paste (eg, Arctic Silver) and then reattach the heat sink.

Only you can decide how much time and money to invest in fixing this elderly system...

Thanks for the reply Ron.

I bought this 4700c in 2005. About 4 years ago, I replaced the power supply. I notice it does get kinda hot. Bur... Also last year I replaced the cooling fan. The machine runs very loud but I've noticed that many 4700c owners complain about the noise. I routinely blow out the case with the compressed air.

Now someone suggested I replace the cmos battery. I did and there's been great improvement. Now machine will run for hours before eventually freezing up. But it still does so. Replacing the battery did wonders but all is not right in Denmark yet.

Thank you for your help

brunetto

Thanks SPEEDSTEP.

I had one of those storefront computer hacks fix something once. He mentioned the capacitors.

The 4700c is over 15 years old and I have only had to replace the power supply one time.

brunetto/Henry

Are you still getting the same effect on the screen when it freezes?

In that case, you might want to apply new thermal paste as I previously suggested since the system is using onboard video and the CPU might be overheating..

Are all drivers up-to-date?