No sound completely.

For the Lords sake, if i don`t have enough problems with this computer, i now have another one, no sound at all.
No sound when playing movies, playing games online, or through my head phones. This only started when i muted my volume, (bottom right on the volume icon on the task-bar, left-clicking and muting).
Obviously i had sound before, but to double check, i opened the Control Panel. Device Manager- Sound Video and Game Controllers, expanded that, and saw that my Realtek High Definition Audio, is still listed.
When i open the Volume Control Options, a box is checked for: "All devices currently playing sound/Speakers".
Can anyone explain what has gone wrong, please.
Thank you.

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 8, 64 bit
Processor: AMD E-300 APU with Radeon(tm) HD Graphics, AMD64 Family 20 Model 2 Stepping 0
Processor Count: 2
RAM: 3678 Mb
Graphics Card: AMD Radeon HD 6300 series Graphics, 384 Mb
Hard Drives: C: Total - 294905 MB, Free - 193468 MB;
Motherboard: TOSHIBA, Portable PC
Antivirus: Windows Defender, Disabled