I upgraded to a powerful GPU and then suffererd intermittent, but mostly not working, startup errors. My motherboard has debug lights, so when I was investigating the internals, I believe it had a CPU fault. So I went off of gut instinct and upgraded to a higher wattage PSU, which was around £90.00. There is no PSU debug lights showing boot problems, I assume because if there is a problem, you wouldn't get the power to light them up! So after I received the new PSU it worked (eventually). At first, I was still getting an error light. This time, as I changed the cable going to the card. I now think the light was signifying a VGA error. You might be blaming me for not being able to interpret the lights, but it wasn't easy. At the end of the day, it wasn't the card, in fact it was the PSU. Just shows you can't beat a hunch.