Hp pavilion slimline s3020n PC the computer says no analog signal the problem is all the time cant run the computer at all.i have not tried to fix the problem myself

Replacing major hardware in a computer makes it a whole new computer. The motherboard is the operative part here that is causing your problem. When you replace a motherboard it becomes a new machine entirely. It won't recognize the recovery CD because it doesn't recognize your computer as the same machine it was loaded on. You will have to buy a new copy of windows to put on your computer.

chech connections. is there power getting to monitor?

Check the video cable connectors, remove the video connectors and reconnect them again.
Check the monitor input settings make sure the input is set to VGA and not to DVI.
Try a different monitor.

Try using F1. Either hold it down as soon as you turn on the computer until you see it entering setup.

http://h10025.www1.hp.com/ewfrf/wc/document?docname=bph06788&tmp_task=solveCategory&lc=en&dlc=en&cc=us&lang=en&product=3376325

The problems is ether the memory or the video card...
Try to take out the memory then start the computer...

one thing you could try is take out the mains power from the back, then take out the bios battery on the motherboard for about 5 mins. this should reset your bios then put them back in and restart your computer. see how you go with that.

Sounds like the graphics card is gone belly up. Try the monitor with another pc or just replace the graphics card.
Hope this helps

Well... try un-plugging the VGA cable... ie., the monitor cable behind the tower...... if u get a message on screen saying No VGA Input... can confirm there is no issues with the monitor...

if you are using graphic card in computer unplug that and connect the VGA cable to normal display card came along with the computer and try...

or if you have another monitor... u can try connecting that to the tower which is not sending the signal to monitor and try....

even then you get the same problem... get an new graphic card... (if you dont have other monitor try with new graphic card)

They are usually in a plastic caady which has a latch on it find the latch and release the caddy hope this helps