Volume acting crazy

My volume on some things today is barely audible; other things regular… When I play news videos, it is barely audible; also when I go to the Cingular wireless log in it is barely audible, but the bell that tells me I have mail in outlook express is normal; the reboot music on windows 98se is normal. My Quicken software that i have attached a wav sound to when it opens, is barely audible and normally it blasts you out.
Any clues? My volume knob on the speakers themselves is turned up to the max. The volume control on the computer itself is at max.

Windows 98 SE
CMI8738/C3DX PCI Audio Device
VIA AC’97 Audio Controller (WDM)