I have no idea what's going on here (no new installs or anything), but a few days ago I noticed I had no sound in TF2 - duly checked my control panel and it tells me I have "No Audio Devices". Ok. So a PC restart later, I boot up tf2 again and all is as normal. Then I quit and am browsing news sites when I realise I have no streaming video sound and iTunes won't even load up.
I check my device manager and the only

Anyway, wiped ATI drivers from my system, reinstalled using latest downloads and still the same problem

Reinstalled the onboard audio drivers also (although no problems shown with them, couldn't hurt...) still same problem

Anyone else had this and have a possible fix?
cheers in advance for any replies.
(system running XP, ATI RadeonHD2900XT, Asus p5wdh deluxe mobo with onboard Realtek audio)
edit: I know there's something weird here because I still hear windows sounds through the speakers (sounds for erroneous clicks and even the logout jingle etc) - this is still with ctrl panel-> Sounds&Audio telling me I have no audio devices.