Hi. I recently brought a HD 4550 for my Dell C521 but when I plug in the card, the monitor doesn't receive any signal. I had a HD 3450 before which worked for about 6 months and then stopped working suddenly. I took it to my local tech shop and they thought my graphics card broke as they successfully installed a Nvidia 6200 LE. (which blow) My original x1300 won't work either - the only card that works is the Nvidia one. It could be that my new card is faulty but I feel that's unlikely. The tech shop told me they didn't know why my ATI cards wouldn't work and they said it couldn't be a driver issue etc. How should I proceed? Thanks.