Volume control is grayed out

My computer was recently attached by a virus that destructs my system, so I decided to reformat for me to start anew.
Everything else is going great except for one. My sound system does not work.
I am using a Windows XP Service Pack 2 machine and a Realtek device.
I do not know if I missed anything right after the reformat, but I am sure that the Realtek Audio driver was installed already.
I have checked the Device Manager, and it shows that my Audio device is working properly, but when I clicked on the volume control, it is grayed out.
Checked the Sound and Audio Devices and it is grayed out as well.
Need help please.
