Buildapc

I built my computer 8 months ago. 6 months later, the mouse pointer started lagging so bad it was unusable. I tried some fixes but nothing really helped. The next day, my computer didn't work. POST says it's the graphics card. Okay, I got a new one. It arrived today and I put it in. Nothing has changed. The fans on the old one worked, so it had power. Did I misread my beeps or do something else wrong. I know enough to build a pc, but not enough to troubleshoot it.

This is my motherboard. It doesn't have onboard graphics.

This is the old graphics card.

This is the new one.

Help!

As requested: 1 long beep, 3 short. No unusual flashing. It powers on fine and everything appears to be working inside, but it does the beeps and doesn't show anything on the monitor. This is the power supply.