I agree that an OP should state if they have asked for help elsewhere and what has been suggested, but as none of those sources have been able to help, then it’s quite natural to ask elsewhere.

Yes, that’s what the rule says.

Good suggestion from mrjimphelps.
I’ve run into the very same problem on several desktop PC’s (not so easy to fix on laptops) If the CMOS battery is dead, there’s no boot data for the USB keyboard or mouse.
It’s easy to check if you have a meter. Place the POS probe to the battery that’s exposed on the motherboard of your desktop PC and the NEG probe on any exposed metal. Your meter should tell you immediately what the CMOS battery voltage is…3volts is normal. If it’s less than that expect BIOS boot problems.

The battery is normally a CR2023 from any supermarket or PC store. If you don’t have a meter, take the PC to your local computer tech and he can check it quickly.

mrjimphelps suggestion to use a PS/2 mouse & PS/2 keyboard is also a good start point if your PC has them on the back of the machine. They are colour coded green and purple with symbols to indicate which is the keyboard socket and which is the mouse socket. Be gentle, the sockets are very easily damaged.. Good luck.

Forgot to mention..
It is possible your power supply is dead so there’s no 5 volts or 12 volts for the motherboard or the USB 5 volts systems. Again easy to check with a meter and one of the power supply cables which support a hard disk drive. The 4 sockets on the end of a cable are black=Neg and the other’s are yellow and red which should be giving 5 volts and 12 volts, which are not critical +/- 10%.
Be careful you don’t short circuit these socket pins when testing. The power supply doesn’t like short circuits !

Another possibility which will check that the power supply is OK, is the BIOS POST (Power on Self Test).

If the POST test is good the PC (most of them) will give one ding ! If no ding’s it could be mean either the MOBO or the power supply is the culprit. Any more ding’s than one, (both short and long ding’s) indicate other problems which means you need to google the BIOS maker & find out what the number of ding’s you heard..mean. You need to count them carefully. A wrong count is very misleading.

I am having that problem. I don’t know if this is situation is the same. I am losing both mouse and keyboard each time I plug my fan into a USB port. When I remove it, the mouse and keyboard resume working. Are the other USB ports in use?

Has it always done that or previously worked – could be a PSU problem ?

I am having that problem. I don’t know if this is situation is the same. I am losing both mouse and keyboard each time I plug my fan into a USB port. When I remove it, the mouse and keyboard resume working. Are the other USB ports in use?

The USB hubs can’t supply more than 5volts @ 500ma max. If your fan is over these figures and especially if it’s plugged into the same hub as the K/B & Mouse then the fan will suck all the available power the hub is capable of supplying.

If the fan doesn’t exceed 5Vx500ma then pick another USB port thats not on the same hub as the K/B & Mouse. To check the hubs in use and available power go to the Device Manager and check each of the USB hub properties.

Also as suggested by Sudo15, your power supply might be suspect especially if it’s 5volt supply is running close to it’s maximum ratings.

I’m assuming it’s a desktop PC and some desktop PSU’s have very little capacity to spare. IE: a 350watt PSU might be near it’s max rating, especially if you’ve added additional cards, HDD, SSD or other hardware etc to the machine since you obtained it.

If a LapTop then try another USB socket for the fan, assuming the LTop power supply has enuf guts to support the fan’s power rating.

not quite the same issue, i had major problem with my usb mouse erratic behavior. Very very irritating. Threats did not work, bouncing it didn’t help, cleaning the lens didn’t help. Adjusting the mouse settings in control panel didn’t help. I was about to teach my mouse to fly, when i decided to try 1 last thing. …i went to the shop and dug out my little glass fiber burnishing brush and cleaned up the usb contacts. Well !!!!!! The little guy has a new lease on life. Works like he just chugged a red bull. Wonderbar.

Well done!