Sound Problem

Ok, This has been troubling me for a long time and I need help. Here are my symptoms:

Sound does not play in a Flash Movie
System Sounds(Logon, Shutdown, Error sounds etc) Do not play
When choosing System Sounds play button is greyed out
MSN Messenger does not play sounds
When playing a defualt sound to test my audio playback the tower beeps and nothing else
Sound play normally through Windows Media Player
Itunes does not play sounds

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I have been looking into this for ages and I still cannot find an answer. I even went out and bought a new soundcard but still no results. Here are some details on my computer:

Windows XP
Realtek AC'97 soundcard (Not using) - Plays Media Player but not system sounds etc.
Trust 5.1 External Surround Sound Card - Plays Media Player but not System sounds etc.
Speakers are embedded in monitor, there are two of them.
Made by Packard Bell

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These are all the detials I have at the moment and I would like somebody to try and help me. So far all the solutions I have tried haven't worked for me and I don't think I can do system restore becuase I have important files that I don't want to lose.

Thanks to anybody that helps. If you need to contact me I will visit this regulary but my emial is andy_NACW@hotmail.co.uk