i don't know if this makes a difference, but you didn't indicate what type of "accessory" you tried to add to your computer.

 

1) was it an "authorized" product, made/intended for use with your particular brand/model PC ?

2) did you follow all indicated directions, in order, in terms of precisely when to connect things, and when to turn-on each item (PC, accessory)?

3) did you need to install any software first,  in order to get your PC to "recognize" the accessory?

4) was the interface/connection a USB-port? or something else?

5) is it possible that you somehow short-circuited (and thereby "fried") something on your PC?...  even a simple STATIC-electric "touch" can do so.

6) have you DISconnected the accessory, to see if your PC functions normally without it?