To answer this correctly, you'll need to supply some additional details.
Does your headset have a USB connection (you mentioned accidentally plugging them into the usb port).
OR does your headset have 3.5 jack(s), for listen and (if it has a microphone), one for speaking.
If your headset is USB and you plugged it into the front of your computer, try to plug it into the back in one of the other USB ports and see if you get the same results.
Also, if you have lots of other items plugged into other USB Ports, the alert/error simply means it's "overloaded". Try disconnecting all but the required devices (keyboard and mouse, if applicable), reboot, and try your headphones again.
If this works, then your computer simply doesn't have enough power to manage all of your USB devices.
In this case, you can purchase a Powered USB Hub, which actually plugs into a wall socket, giving power to the USB devices you'll plug into it.
If none of these options work, please reply, and we'll try some other neat tricks.
Good Luck!
Additional details (By: Stoxvell):
My headphones have three features: 1- A sound cord that plugs into the sound place(Not sure what it's called). 2- A speech cord that plugs into the speech place(Not sure what it's called either). 3- A mic for speaking into. I accidentally plugged the sound cord into the USB port and the a popup in the bottom right corner of the screen appeared saying something like, "WARNING!! A USB port has overloaded!" and then I think it also might have said, "Please check that your devices are working properly," but I'm not sure. That's all there is to it. Oh and don't forget that each of the headphones (the things that let you hear the sound) are the round kind that are connected by a by a plastic band that can extend and detract to fit your head. There is also a little sound control box on the cord where the cords for speech and hearing meet. I hope that's enough details. Now for the question I meant to ask: Is it possible to fix the sound on my headphones?
no probably not , you might have overloaded it with to much power
It likely that you plugged your headphones into the wrong jack. There should be a jack for your headphones on your computer that has the head-phones label on it, not the one with speakers or for a microphone.
If the headphones work on a PC in the US, then they will work on UK PCs. However if your headphones come from a cell phone, then they will not.
I have a hcl head phone I have plugged it on but does not work
A good standard procedure for checking a possible hardware failure of this nature: First test the computer and the peripheral (headphones in this case). Plug another set of headphones or a speaker into the same jack you plugged the headphones into. Next, plug the headphones into another computer or mp3 player. This will help determine if it's one or the other that is faulty. Check ALL your volume controls. In Windows, there are multiple volume options. In your system tray, there is a speaker icon you can right-click on and select "volume options." Make sure you don't have something muted there. If you put your headphones into another computer and get sound, but you try a pair of headphones in your computer and nothign works you may have a faulty jack. Get a pair of phones you know work for certain, plug them into the computer. Do you get any hissing or intereference? If so, it is likely the computer. Try very gently wiggling the part of the headphones that plugs into the jack around while it's plugged in. Do you get static or popping sounds? It is likely the jack in need of repair if you do.
Definately
Make sure the computer is not in "mute" mode.
Headphones that don't need to be plugged in. No wires = wireless
Monitor is not plugged in or monitor is not plugged in to computer
there may be some issues go see an apple store to check it out.
Well I had my MP3 player plugged into some computer speakers and it didn't die, this was the same plug you find on headphones and earphones, so if it fits it should work. It probably won't work with stereo speakers but I haven't tested that yet.
No some can be plugged into speakers.