Since this is a new PC, best to call Dell support. If you have a separate video card you can open the case and reseat the card in case it came loose in transit. Also, if it has a separate PCIe power connector on the Video card make sure that is fully connected. But, that is about the only thing you can try. Reseat-with the PC powered off unplug the card and then reinstall it making sure it's fully and correctly seated.
Dimension E510 with D925 CPU and Vista Home 32 bit
Home Built PC with Q6600 CPU - Windows 7 64 bit Professional
Sonar 8.5 Producer DAW Software/Focusrite Saffire Pro 40 Recording Interface