See if the Plug and Play (plug and pray) service is set to automatically start and also see if it is running.
Start -> run -> services.msc
Double click on Plug and Play. Set to Automatic and click start if it isn't running already.
If that was turned off or disabled, then you might need to restart your computer for the setting to take effect.
Note, on my XP x64 workstation, I cannot disable or turn off the Plug and Play service.
One further note, if those commands don't work in Regular mode, try in Safe Mode.
