"No speakers or headphones are plugged in" Error

I'm not too savvy with computers, so I don't know what the hell is going on or how to fix this! I have an HP Pavilion DV4-1428DX Entertainment Notebook. The sound was working perfectly fine at about 6am this morning, and around 10am it just stopped working. The speaker icon on the laptop itself(Touch it to mute or unmute sound) is red and touching it doesn't unmute. The speaker icon on the right side at the bottom of the screen(Near the clock) has a red X on it. I tried troubleshooting by clicking on the speaker icon, and no solutions or anything came up. I did a quick google search and it seems this is a common error, but I can't seem to find teh solution to help me out at all. I tried calling Microsoft since I run Windows, they told me to call HP. I call HP, and after getting hung up on three times, and then getting a guy who spoke almost no English whatsoever, I was told that my warranty has run out, and although they know exactly what is wrong and how to help me fix it, they cannot give me the answer unless I pay for a $15 per month maintenance plan, and call me old-fashioned or cheap, but I'm not gonna pay $15 to have a guy give me the answer. I'm not sure what exactly my operating system is, because in my control panel, it says I run Windows 7 Home Premium 64-bit, and if I use the HP website to scan my laptop for problems, it says I run Windows 7 Home Premium 64-bit, but if I go to the BIOS menu on start up, it says I run Windows Vista, and the sticker on my laptop says Windows Vista as well, so I don't know what to go with. I know very little about what goes on with laptops, so if anybody could help solve this and walk me through how to resolve this issue, I'd be forever grateful.

Any ideas guys?

Since this worked and now does not work, the first step is to use System Restore and restore the system back to a date when it did work. System Restore can be accessed by Start/Programs/Accessories/System Tools. System Restore will not delete any user data or e-mails and there is an undo function if it doesn't help.