Speaker/headphone problem

If I reboot when the speakers aren't plugged, and plug them afterwards, they won't work. Same if I unplug them with the computer on and then I plug them again: they won't work. Same happens with the headphones. Anybody know what's the problem? Thanks in advance.

Driver issue. Is it onboard sound?

What kind of headphones / speakers? Might be USB.. Still, a driver issue sounds likely. Do you have the proper drivers installed for your sound card? Also, if it's the standard Realtek that everyone has, did you install the control application? Sometimes you have to tell the sound card what audio jack to use. ~MiSfit

Thanks to both of you. I reinstalled the drivers and now everything works fine.