I'm a complete novice when it comes to working on computers...so please be gentle.
I was going to fit a new graphics card. I removed the original Quadro FX 3450 and found that I had been sent the wrong replacement. So I put the original back and now my computer will not boot up.
I get to the blue Windows page with the F9, F10 and F12 options then it goes back to the black and white page that says the system may have been shut down accidentally and will re-start in 30 seconds or whatever..