If your computer starts up to a blank screen and you know the monitor & video card to be good then it could be that the screen refresh rate is set too high for the monitors you are using. when you turn on your computer press F8(usually this is the correct key to press) and this will take you to the boot menu. Select Last known good configuration and this will reset your computer to a time when it worked.
Hope this works.
Do you hear any beeps when you turn it on ?
we should first check the Motherboard ---
unplug computer --- open case --- remove all Ram ( Memory ) then turn on computer --it should beep ,, if it does then we can continue , if not then the Motherboard is not reading the memory configuration and would need to be replaced --
Sorry for the bad news ---
If you need further assistance please let me know ---
When did this problem start occuring? Did you swap out any hardware or download anything? What kind of video port do you use? - AGP, PCI or PCI-E?
If it is a PCI Video Card, do you have an extra PCI slot on that motherboard? If so have you tried swapping the card to a different slot?
Is the monitor LED green or orange when you start up the computer?
Does your monitor say anything about display not found?
Have you checked the monitor cable for any broken or bent pins?
What is the brand and model of monitor?
Something to try ---
Your Bios may have been corrupted from exchanging the video cards --- so I would suggest clearing the Cmos and force the computer to re-read the configuration --- or it could be that the battery is failing, and needs to be replaced ---
to reset Cmos ---
unplug computer --- open case -- look for a small flat ( looks like a watch battery ) and remove -- DO NOT FORCE IT --- otherwise you could use the Cmos reset jumper --- it is located not too far from the battery --- just change the jumper to clear for 30 secs -- and place it back --- now close computer -- plug in and turn on -- it will now re-configure your Cmos --- with the new video card ----
Good Luck !
to better assist you,, could you tell me the make and model computer --- and if possible which BIOS version you are using ?
according to the beep code ----
reseat the video card or bad video card --- reseat the Ram or bad Ram --- insert one stick at a time and see if it still beeps ---
that is very possible,,, it could have been power surged --- was the computer plugged in when you installed the memory and the video card ?
when it first occurred it could have been a bad video card or a bad ram stick -- but then the replacement could have been damaged by a power surge from the computer being plugged in --- it has happened before --- one problem compounds on another ---