This is a "point of sale" PC. It had two expansion cards: 12volt USB and PCIE to PCI riser. I ran memtest on it and all was fine.
I wish to to use it as a plain desktop PC, so removed the two specialised cards. Now it does not boot. The DVD drive flashes when switched on, that is about all that happens. The keyboard and mouse do not light up. There are no beeps nor red LEDs on the front panel. After a while the CPU fan goes to full speed. I cleared CMOS, but this did not help. I removed the RAM and that works in another Sandy Bridge PC. I downloaded the Maintenance and Service manual, and it seems to me that the PCIE cards are optional, no mention that they are needed to run the PC. I would expect it would have a POST message like "interface card is missing" if they were required. Unfortunately those cards were damaged in accident, and I cannot put them back to confirm that.
Be alert for scammers posting fake support phone numbers and/or email addresses on the community. If you think you have received a fake HP Support message, please report it to us by clicking on "Flag Post".