I found the solution to my problem. After browsing through a forum, someone mentioned a program I had uninstalled that had come with my Gateway. I realized my sound didn't work after this and reinstalled the program, and now it works again.
Good thing I don't have to reinstall my OS or sound card now.
I have a Gateway AMD Athlon 64 X2 Processor 4200 that's operating system is Windows XP. I bought it recently and just got around to setting it up yesterday. I installed many of the same programs I had on my old computer. The sound worked perfectly fine until I woke up this morning and a wizard popped up and asked me about software concerning ''Multimedia Audio Controller.'' I had installed a webcam and a scanner and tried to run both of its software programs even though I had yesterday but it didn't work with it. Now my computer is making internal noises when a pop-up message comes up or it shuts down or whatever.
So anyway, more details: my speakers are the kind that you plug into the speaker jack and then into the USB jack. Maybe it was responding weirdly because of that? Also, I am the only one on the computer, so no one's been fooling around with it. I did update iTunes right before the wizard popped up though.
What I have done concerning this: I've done a system restore to yesterday, but the wizard popped up again and the speakers still won't work. I opened up Windows Media Player and tried to play a song, but it wouldn't work. I also tried this after I plugged in my headphones, but it still didn't work. I've been trying to find a good tutorial, but most of them are concerning if the computer recognizes the speakers--my computer does not recognize my speakers. I also hooked up other speakers to it, and alas, no luck.
If more information is needed, I can surely provide it, but I don't know what the sound card's model is. I can find out, though.