Please help me, why don't i have a sound device installed?

My speakers worked fine a few hours ago. Now they dont. My pc told me that
I dont have a sound device installed... Also, when I restarted the computer,
I was informed that there was "new hardware" on it. I tried to install the
new hardware, which i think meant the speakers, the wizard couldn't find the
software. It said to insert a disk if the hardware came with one. The thing
is, there is no disk, the speakers came with my computer and the only disk
that came with it was a system recovery thing... Before this problem i had
been trying to delete things from my pc which i won't do anymore because i
have no idea what i am doing. but luckily i had not emptied my recycle bin.
i restored all deleted files and restarted my pc but it still couldn't find
the software... what do i do? i don't know about computers...