Try to plugin some memory stick to check
If there are problems
# Start Windows guest OS, go to "Start" -> "Control Panel" -> "System" -> "Device Manager" and uninstall all devices under the "Universal Serial Bus Controllers" (right-click the devices).
# Shut down your VM.
# In VM Configuration Editor, delete the USB Controller and start Windows guest OS again.
# Wait 5-10 minutes until Windows finishes the driver setup.
# Shut down Windows.
# Add "USB Controller" back to your VM configuration and start Windows again