Vista Link and Sound Device Problem

Hi,

Few days back, I was installing/uninstalling some programs. I don't
know
what went wrong, suddenly I found the links in "Computer" are not
working.
When I open "My Computer" ("Computer" in Vista), all the links like
"Device
Manager", "Remote Settings" etc are not working. It says for "Device
Manager" - "Windows cannot find '%SystemRoot%\\system32\devmgmt.msc".
However, if I run the same command from a DOS window, it exists. This
is
same for all the other links.

My sound icon in the task bar also marked a permanent red cross. If I
open
Volume Mixer, it says - No audio device found. But I can still hear
sound.
I don't know what to do. Please help me.

Thanks and regards,
Jaydip Chakrabarty