are all graphic cards compatible with every system? I don't know what type of mother board i have T-T I didn't build it. It's a dell computer. And I think the mother board was already there. Because it says DELL on it hahaha but are all graphic cards compatible with it?
No, not all graphics cards are compatible with all systems. You need to make sure you have the power supply to support it and the slot on your motherboard to put it into. Graphics cards can go into PCI, AGP, or PCI-E slots, newer ones will go into PCI-E slots.
Check to see what slots you have on your motherboard, or if you know what the model number of the dell is post that too and we can check.
You also need to check the size of the power supply and how many amps it has on the 12v leg. Computer manufacturers often size the PSU to the unit sold and don't provide much extra power for upgrades. This is particular relevant to video card upgrades since they are major power users.
For general help on upgrading graphics cards you might want to go to upgradevideocards.com to see the info and instructions they have.