I bought a used AMD Radeon RX 7800 XT and installed it in my PC, but Windows doesn't detect it at all. I've tried reinstalling the drivers several times, updating the BIOS, and even putting it in another PCI-E slot, but nothing. What am I doing wrong?
The graphics card probably comes with outdated or corrupted drivers if it's being used, so try completely uninstalling everything (the GPU and drivers via Device Manager) and then install a fresh version of AMD drivers from scratch, not just update. Before that check if the PCI-E slot is actually working (test with another card if you have one) and if the 16-pin power cable is properly seated in the GPU - this is the most common mistake and it goes unnoticed. If it still doesn't show up, the card might have poor contact or be damaged at the connector, in that case it's worth cleaning the gold contacts with a soft eraser or a slightly damp cloth.
Try checking if the card is making direct contact with the slot, carefully clean the pins on both the card and slot, and verify that the power supply is properly feeding the PCIe power connectors. If it still doesn't show up, the card might be burned out even if it's been used recently.
First of all, check if the power connector (those 6 or 8-pin cables) is plugged in correctly into the card. Like, push it in until you hear the "click", because sometimes it sits loose and Windows doesn't even see the GPU exists. I had a case at home where the card was technically installed but the power cables weren't seated properly, and the PC just ignored it like it wasn't there. When I plugged the cables in right, boom, it recognized it right away.
Another important thing: if your PSU doesn't have enough power (that RX 7800 XT draws a lot of energy), Windows might detect the card but incompletely or glitchy. If you're not sure about your PSU's wattage, check the label on it. The recommendation is around 700W or more for that card. Also try cleaning the gold contacts on the card with a dry, soft cloth, and dust out the PCI-E slot. Sometimes crud builds up that prevents contact.
One last thing: completely remove all old drivers (Device Manager > Display adapters > right-click > Uninstall device, check the "delete driver software" option) and restart with nothing installed. Then download the latest drivers straight from AMD's website. If it still doesn't recognize it, the card might be damaged (it's used, so it's possible), but test all this first.
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