OK, the easy one first.
Go back into msconfig and uncheck the following entries:
nwiz (used for advanced graphics settings such as multiple monitors, virtual desktops and so on)
NvMcTray (Provides quick access to video properties - you can do this through Control Panel if you need it)
Reader_sl (Speeds up the loading of PDF files)
Reboot (legacy utility from older versions of Wiindows).
Click OK and choose to reboot the computer.
These can all be turned on again by checking the appropriate box in msconfig if needed, so no harm done. However, they all consume resources and so are better turned off.
As for the sound problem, download
Belarc Advisor , run the downloaded file (named Advisor.exe) and wait a couple of minutes while it gathers the data from your computer. A web page will appear (this is local to your machine, not on the internet). Look for the 'Multimedia' section of the report and let us know the sound device if one is found (for instance, mine is shown as 'Realtek AC'97 Audio').
Please note that a lot of the keys and serial numbers for your software and operating system will be included in this report. It would be useful to print a copy for future reference but please make sure you don't publish them in a forum. :)
If nothing is showing in the Multimedia section then go to Start, Control Panel, Add Hardware, click Next, check the button to say you have connected the hardware, click Next. On the next screen click 'Add a new hardware device' (at the bottom of the list) and click Next. Choose to 'Search for and install the hardware automatically', click Next and see if the soundcard is picked up automatically - it should be as it has already been installed previously.
Let us know how it goes.