Windows XP volume control problem

Not sure where to post this so I'll try here 1st.

I have an HP Compaq nx5000 notebook, running Windows XP Pro.
The volume icon has disappeared from the task bar, and I can't get it back by going through the control panel etc. Also the mute and volume buttons on the front of my laptop are not working. I do seem to have sound working but don't seem to have any volume control (i can change the volume within itunes and real player etc, but can't change the actual speakers/computer volume).
I have tried reinstalling the soundmax driver off the "driver recovery" cd that came with the laptop, but no success.
Have done a bit of googling and found this:
http://support.microsoft.com/?kbid=319095
I have followed it and expanded the relevant file from the XP cd with also no success, although searches told me I already had sndvol32.exe in windows\system 32 anyway.

Finally, I just tried a system restore and when the computer restarted it told me it was unable to complete the restore.

So has anyone got any idea what is wrong, and more importantly how to fix it?