Hi everyone! I need some help figuring out what's going on with USB ports not working. I hope I provide enough information. OK, so the computer is a Dell XPS, couple years old. The USB ports are not working. Bios does not recognize that a keyboard is plugged in - unable to enter Bios. Laser mice do not light up when plugged in. I added a USB PCI card. This too does not work. Still no light on laser mouse. I'm pretty puzzled. I tested the PSU. -5 tests bad. I know that USB supplies 5v - so I order a replacement Dell PSU. The -5 on the new PSU also tests bad. USB ports still do not work with the new PSU. I've ran into this same scenario before and am trying to learn what's going on. My view now is that the motherboard could be bad. But before buying a new motherboard, I am asking for some help/insight. Is it common for power supplies to have -5 test bad? Is this an actual problem with the psu or is it the tester misreading? Why would the PCI USB card not work as well? Thanks for any help!

I recall someone posting in the past that the -5V is only used by motherboards with ISA slots. Those are virtually non-existent in modern motherboards so it is unlikely the powersupply is your problem. I'm inclined to look for missing chipset drivers as the reason your USB ports aren't working. Check in devicemanager to see if any USB controllers are listed and if any yellow ?s are evident. Goin' Fishin' (Some day)

Thanks for the response. The keyboard does not work during POST, so drivers would be a no-go. This is a USB only motherboard (no PS/2 ports). Also, I've pulled the battery to reset BIOS, just in case they got disabled.