Can you tell us what the specs of the machine are? Processor, Video card, RAM etc. If it's windows, go to the run command and type dxdiag. This will give you all the info we need.
Most modern machines should be able to at least work with HD to a base level. What are you trying to do to it? Are you rendering it out and then it gets pixelated? How do you import it? Does it look the same when you view the file on your machine?