Volume Control in Laptop Going Down

I am running a Windows XP PC with IDT HD Audio on my laptop. While using it, I noticed that when I turned the volume meter to the highest level, it will slowly decrease. I searched for possible solutions in Google but most forums and articles are advising me to uninstall and re-install the sound drivers. I don't know much about computers and I don't want to make things worst so can someone please help me in resolving this issue?
Thanks.
