I have an HP 754N running XP. After not using for about 6 months I hooked up and started. It starts and runs about 30 seconds and shuts off. If I try to start it runs maybe 10 seconds and shuts down. 3rd try runs 1 second. If I wait 10 or 15 seconds it's back to the 30 seconds. I replaced power supply, no change. I tried different HD same problem. I'm at a loss. What is left? I have a newer Gateway that I am using and the old XP is just for a few things Xp does that Win 10 doesn't. Friend suggested heat, but 30 seconds? It is kinda dusty, but 30 seconds?