I have a problem with my desktop PC. The USB ports are not working so I can't use my keyboard or mouse. I'm not sure if it has any connection with this, but today I tried installing a SSD to my system with no luck. While doing that, I set the BIOS to AHCI as I read that would be the most optimal. Well, I kept getting errors trying to install Win7 to the SSD so I decided to save it for a later time. Then I turned off my PC, unplugged the SSD and plugged my HDD back in. On boot up, I entered BIOS and set settings to default. After this my USB ports stopped working.. I have tried turning off my system, unplugging the powercord and the CMOS battery for at least 15 minutes with no luck. I have also tried plugging my keyboard into every single USB port my PC has. I can't even enter BIOS or press F8 to enter safe mode now. Any suggestions? I'm using WinXP and my motherboard is a Gigabyte GA-870A-UD3.