Right, well, I've read some posts on here about Power Supply problems, but haven't come across any with the same problem as mine - basically because it's 3 in the morning and I'm too tired to read through all of them. Besides, who would read them all anyway, right? Anyhoo, here's my problem. I have an HP Slimline pc (model #'s in the title), and for those of you who have owned SFF (small form factor) pc's, you all know that they come with pint-sized PSU's. Granted, I am impressed by this tiny machine's will to live - by that I mean it is powering a ATI HD Radeon 4650 on a 160W PSU - I'm lucky this thing is still kicking. So, in order to save this PSU a bit, I've wanted to upgrade to a higher powered unit. I've even bought an adapter for the main connector to accommodate this change. I've used a Corsair 550W PSU, and also a hec Compucase HP585D 585W PSU as upgrades to the tiny power unit, BUT, both have failed! By 'failed', I mean the Slimline shuts off shortly after powering on the system, and sometimes it has issues even powering up the motherboard. I suspect this because the optical drive spins up, but the fans on the CPU and the Radeon GPU don't do anything.... sometimes. Again, both 500+W PSU's stop working after the first day, and when I go to plug back in the Slimline's 160W unit, the system has no issue's what-so-ever. So, why am I putting myself through all of this? Well, as others have done, I'm trying to allow for more power to upgrade the video card. A little voice in my head has finally chimed in and told me to leave the system the way it is, and I'm about to listen to it. My reason for posting here is to see if anyone would happen to know why I'm having these PSU problems. For reference, the motherboard model # is M2N61-AR, a mini-ITX board. Its RAM is the standard 4GB that came with it. The CPU has been upgraded to a Dual core 2.9Ghz Processor from a 2.7Ghz. The GPU is the Radeon HD 4650, 1GB version with DVI and HDMI in LP mode. The only other things the PSU powers directly is the DVD drive, and the hard drive. My thoughts for upgrades were to install an ATI HD Radeon 5570, hense the reason for the bigger PSU. And to accommodate the physical change, I was going to put all these parts into an Antec Six-hundred case and get a Card Reader to replace the one that's strictly fitted for the Slimline case. But, all that's hampered by the fact that no PSU upgrades will continue working on this tiny system! All thoughts, suggestions, etc. are welcomed. Also, if the guru's of the site need more info, I can provide what you need to know, and even get pics if that helps too. Thanks in advance!