usb ports dead

[steve20841]

I have a Dell XPS 420 that originally came with Windows Vista in 2007.  This pc has been upgraded in most ways.  New hard drive, new memory modules, new power supply and running Windows 7 (32 bit).    As a back up reference pc, it's used mostly for web based programs.  Logitech wireless keyboard and mouse used.  All peripherals' run thru the eight USB ports (keyboard, mouse, printers, etc).   No problems in the last year until last week while booting up, an error screen stated "no keyboard found.  Started out with simple checks like rebooting, installed fresh batteries in the keyboard and mouse, tried all 8 usb ports, even went to a wired keyboard.    Even switched out the keyboards with a working pc.   They worked fine.  No PS2 ports to work with. 
This is where I am now stumped.   

I have two other working pc's that are Windows 7 64 bit and an older Windows XP units.  I pulled the hard drive from the broke pc and attached it to one of my working pc to look at all the files.  I'm not sure how to determine if it's hardware related, software related or motherboard related. 

Any suggestions would be appreciated.  Thank you

[DaveLembke]

If the USB devices attach directly to the PC to where there is no HUB in between for 8 ports, then it could be either hardware or driver related.

First only have the keyboard and mouse connected with all other USB devices disconnected. This will remove the possibility of a USB power draw overload condition causing the loss of all USB. If problem remains then proceed forward with next step, otherwise if mouse and keyboard are working then something else connected is possibly overloading the USB 5v power and you can attach 1 device at a time until the USB cuts out again. Removing the device that causes it to overload/cut out should bring USB back within a few minutes otherwise a reboot may be required. Try this device that overloads the USB on the troubled computer on another computer if you want to confirm its problem.

Unfortunately with the model that is USB only and no PS2 port for keyboard/mouse, the only suggestion I have to determine if its hardware or driver related is to burn a Linux DVD off of another computer such as the Knoppix Live Linux Distro DVD, and boot this troubled computer off of the Linux DVD Disc assuming it has a DVD-ROM drive. If your keyboard and mouse work after the disc loads then its not hardware related. If you still have no keyboard or mouse then its most likely hardware related.

The good thing is that if it is hardware related you can fix it by installing a USB card, but most PCI USB cards max out at 4 ports so if you need 8 ports, you will need to buy a USB hub to go along with it to give you the necessary port count.

If you find that it is driver related because the USB ports work fine under Knoppix Linux, then I'd boot the system off of the system recovery set and perform a repair installation which will correct for a bad USB driver. Then you should be all set.

[SuperDave]

Sometimes disconnecting and reconnecting the power supply clears this problem with USB ports.