My cruzer 4 mb usb stick is suddenly not recognized by the computer

With usb drives getting plugged and unplugged all the time, the connections inside of them and the connections to the usb port will get worn down.

my suggestion, plug it in, place some pressure on the drive (either pushing down or down) and see if the connection comes back. this has work for me in the past. if you get a connection, maintain the pressure, and copy everything on to the computer.

ditch the drive and get a new one.

This may have many causes. first possibility: the stick is dead and needs replacement. second: there may be a problem with the usb-port or -controller. if you connect a different usb device to the same port as the stick, and it's recognised, the usb- port is fine and it surely will be the stick which is broken. if the other device isn't recognised either, it's a usb related problem. in this case you should verify if all settings for usb in the BIOS are enabled, if the usb-controller in device manager has been installed supposedly. if not, reinstall, reboot and try again. if this does not work, you need to replace your computer's system board