Thanks to everyone who responded. Apparently the first video card I tried was defective. I only changed the video card - no mods or other upgrades needed. Windows recognized the card and auto-installed the drivers. I did not download drivers from Nvidia. The new card has been stable with 4k resolution 3840x2160 - so nice to have the screen real estate!  This Alienware X51 has served me well for over a decade. Upgrading the GPU to GTX960 and hard drive to SSD has made this old PC very responsive for modern business apps and general browsing, plus watching 4k videos on YouTube. It's too bad Microsoft is forcing us to retire otherwise good hardware by ending Windows 10 security patches in 2025 and making Windows 11 requirements incompatible with the X51. Maybe someone here can figure out a way? I may upgrade the RAM from 8GB to 16GB but I'm not sure I'd notice a difference. I'm very pleased with this X51! Alienware X51 R1 (2012 OG)i7 2600 CPU330 watt power supplyNvidia GeForce GTX 960Crucial 256GB SSD8GB memoryA14 BiosWindows 10 21H2
Wanting to upgrade the graphics on my OG Alienware x51 R1 (i7 2600 CPU, 330 watt power supply, A14 Bios, Windows 10  21H2). It originally came with the Nvidia GTX 555 graphics card which failed years ago - have been using the basic onboard HDMI since. Now I have a 4k monitor but the onboard card does output beyond 1080p. Searching the forum I found the 'safest' plug and play graphics card upgrade is the GTX 960 so I bought a used one (PNY). After installing the card and booting into the OS, Windows auto installed the Nvidia driver and I was able to change the resolution to 4k. Things were fine for a few minutes and then the display became pixelated (shown below). I have tried the latest driver from Nvidia's website, and also tried their automatic update utility, but having the same failure. Is this a hardware issue with the PNY GPU card itself or something do with the driver? Appreciate any help - trying to keep this system relevant for my needs and save electronic waste!   [IMAGE]  
X51 R1, PNY GTX 960 GPU upgrade failure :-(