I wanted to change my video card as the old one's fan became very noisy. The old one was an Nvidia GeForce, the new one is ASUS HD 5450
The PC was working fine without any problem. After I swapped the video cards, it stopped booting. It works for a few seconds, the fans start, etc. Then, it stops. After a second or two, it tries again, and again and again...
I checked the PSU (even though the new card is supposed to consume less power), it is rated for 500W.
I swapped the cards back (installed the old video card), the problem persisted. This I don't understand, what could have happened??
I tried clearing the CMOS, as it is usually suggested in situations like this. But, I am not sure if I did it properly.
I built this PC 6 years ago. The motherboard is gigabyte ga-ep45t-ds3r, the CPU is a socket type Intel (if it is really important, I can try to find out more).
Very few power supplies are warrantied for more than 5 years, there is a reason for that. It would seem to me that the PSU has died (or is in the process of dying). If you have a digital multimeter, I would suggest testing the PSU (especially the 12V rail(s)).
Understand here that it is not a given that the PSU is the problem, just my first thought when considering your issues.
You may also check to make sure all power connections are securely attached to the motherboard and none of the wires are loose at the connectors. While you're in there, check also to ensure the ram and video card are firmly seated too.
Hope it helps
Can you get into the BIOS? If so will the system run clean for a few mins in the bios without the "works for a few seconds, the fans start, etc. Then, it stops. After a second or two, it tries again, and again and again.." behavior?
If not then standard debugging is to pull parts until the system posts. Let us know if you can't get to the bios and someone will give detailled instructions and point you to the 'no boot' sticky post.
If the BIOS runs ok, then try the following. (Sometime when you swap from nvidia to amd or visa-versa things get really ugly.)
Suggest you re-install old video card. Boot into safe mode (google safe mode to get instructions how to do that). Delete all nvida and Amd video drivers from uninstall programs in control panel. Get rid of any software that seems linked to either nvidia or amd. That leaves you running the old card with a standard windows VGA driver. Then shutdown cleanly and swap the cards. After power up reinstall the drivers for the AMD card and see if the system runs cleanly.
I used the "paper clip" trick, and checked the PSU whether it was dead. That is disconnecting all the connectors, shorting the green and black, then checking the voltages with a multimeter. All the voltage values seemed to be correct. Then, I cleaned the CPU cooling fan, made sure the connectors back in place tightly, and memories are also tight in place. It worked. I don't know what step solved the problem, but it is working now.