Sound not working!

I have no idea how to get my sound working, I've tried everything I can think of.
These are my specs.


Field Value
Computer
Operating System Microsoft Windows XP Home Edition
OS Service Pack Service Pack 3
DirectX 4.09.00.0904 (DirectX 9.0c)
Computer Name ---------
User Name --------------


Motherboard
CPU Type Unknown, 3000 MHz
Motherboard Name Unknown
Motherboard Chipset Unknown
System Memory 3328 MB
BIOS Type AMI (06/18/09)
Communication Port Communications Port (COM1)


Display
Video Adapter ATI Radeon HD 4800 Series (1024 MB)
Video Adapter ATI Radeon HD 4800 Series (1024 MB)
Monitor Plug and Play Monitor [NoDB] (B6804573026)


Multimedia
Audio Adapter ATI HD Audio rear output

Storage
IDE Controller Standard Dual Channel PCI IDE Controller
IDE Controller Standard Dual Channel PCI IDE Controller
Disk Drive ST3500418AS (465 GB, IDE)
Optical Drive HL-DT-ST DVD-RAM GH22NP20
SMART Hard Disks Status OK


Partitions
C: (NTFS) 476929 MB (466256 MB free)


Input
Keyboard HID Keyboard Device
Mouse HID-compliant mouse


Network
Network Adapter Atheros AR8121/AR8113/AR8114 PCI-E Ethernet Controller (192.168.1.7)

Peripherals
Printer EPSON Stylus TX400 Series
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB1 Controller Standard OpenHCD USB Host Controller [NoDB]
USB2 Controller Standard Enhanced PCI to USB Host Controller [NoDB]
USB2 Controller Standard Enhanced PCI to USB Host Controller [NoDB]
USB Device Apple iPod
USB Device USB Audio Device
USB Device USB camera
USB Device USB Composite Device
USB Device USB Composite Device
USB Device USB Human Interface Device
USB Device USB Human Interface Device
USB Device USB Human Interface Device