Windows reverts to classic view and will not show sound controls

Here's my newest Windows frustration. When I boot up,I see the desktop picture for the longest time before it finally loads the task bar. Most of the time, it comes up in classic view, sometimes it doesn't. When it does, just wait a minute and it changes to classic. The whole time it has sounds at startup because I hear the Windows start sound but I don't have a volume icon on the system tray and the device manager says no hardware installed. I can install the creative drivers or just rollback the driver for sound but when I reboot, all is back the way it was before.
I opened ms services and found themes on automatic,but not running. When I start the service, it starts and then shuts down. Sometimes the classic view gives way to XP view, sometimes it don't.
I tried to find the problem without success and then attempted a repair install of XP. After booting from the CD and choosing the second repair option, I got a message stating no previous version of Windows was found. I'm really trying to avoid a complete reinstall of XP because I have a lot of programs installed which is very time consuming to reinstall all of them.
I've already run the usual scans for bugs and bots and found nothing so, does anybody out there know what I did to it this time?

 

Thanks Arie

I had already run SFC but it changed nothing. I checked out the link you reccomended and found the settings were correct already. I rebooted and everything came up ok. I don't know what changed. I'll just wait and see if it last.

Thanks again,
Mark