On boot, the pc usb's are not working

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I was given a Optiplex 760 and on boot, the pc usb's are not working, not possible to enter bios as no usb works.

I have tried various types of hardware in usb ports and no response

All lights are green on front of the pc

on pc there are no ps/2 ports

PC will boot and flash screen of Optiplex 760 is displayed next pc gives out a warning that no usb keyboard is found.

Any idea?

Please help.

Thanks!

I didn't find the right solution from the Internet.

References en.community.dell.com/support-forums/desktop/f/3514/t/19502797

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