Went to a local computer show with a friend. Working on building him a ccomputer. Any ways, he got hold of an HP pavilion 7850. The machine had been caught in a lightning storm and the only pieces that worked were the Processor, Ram, floppy and cd-roms. The machine had a PIII 933mhz in it. The motherboard was shot. We bought an HP vectra VL400 MT for 130$ and an axio X5 series case. We got home gutted the HP vectra and the Pavilion. Everything went together just fine. except one problem, the axio case comes with a 480 watt PSU and the motherbaord out of the HP vectra comes up with an error and does not let me boot unless the PSU fan is pluged into the motherboard. I pulled the power supply from the HP vectra and plugeed it in to the Axio case and the machine came up just fine. This is yet another reason I build my computer from scratch normally but my friend is on a budget. The machine ended up being a PIII 933mhz with 382 megs of ram and a 20 gig hard drive. I can't install windows until I trick the HP vectra motherboard to think the fan is running. Is this a proprietory thing or am I just not doing something correctly? I pulled the cover off of the power supply out of the HP vectra and found the cables for the PSU fan come in from the motherboard and go into some kind of circuit and then go out to the fan. My father is an electronic technician and could easily trick the machine if he knew how the circuit worked or what the circuit does. Any ideas?