This is a real doozie! Dell T7500 workstation. Began with both front fans ramping up slowly from normal slow speed to full on. The computer seemed to operate normally. POST said the fan was defective. I replaced every fan in the unit except or the one in the power supply. No change. I replaced the video card with an unused Nvidia Quadra 4000. No change. I unplugged the hard drive. No change. At this point I am a bit desperate. I spoke to a technician that said the motherboard was the trouble. I then replaced the MB with a tested used one. Again...same problem. The ONLY components left is the power supply and the ram memory. So, I had an unused DEll identical part number PS available. After install? You guessed it. Same problem. Then the last thing I tried was a tested cpu that had identical numbers and specs. Again, a waste of time and money. ONLY the ram is left. I tested it using the long test and it shows as OK. Where do I turn at this point?