Helppp...stupid computer speakers.

yeahyeah

i dont understand this:
ok my speakers are plugged in,
they work with my ipod and stuff.
i plugged them in to my computer and checked it and it says that the device is working propely,
then when i go to change the volume On the comptuer it says there is no speakers,
and on the internet and everywhere i cant listen to anything casue it wont workk.. :S
the only thing that i can hear is msn sounds and computer sounds like when you restart your compuer.
It wa Perfectly fine the other day?:S

Also, when my speakers stopped working around the same time, on the bottem of my computer where the start button and stuff is, part of it turns gray and stays like it, and i have windows xp and its suposed to be blue,and i never changed it or anything?

How do i fix thiss?
its making me soo madd.