Please try this Microsoft Fix-it which may diagnose and troubleshoot the problem.
If this does not help, you can try to uninstall and re-install the audio drivers.
If the issue still persists, you can try to disable the start up programs and services which can affect the volume control such as Skype. Here is a Microsoft article on how to perform a clean boot.
Ensure that the device volume is at the maximum as shown in the image. Moreover, the speakers volume should also be at the maximum as shown in the image. To access Sound properties, go to Control Panel, select 'Sound and Audio Devices'.
If you are using a multimedia keyboard, ensure that the volume keys on the keyboard are not stuck.
Also, which applications when switched cause this issue?
Thanks and Regards,
Every time I switch applications, the system volume level on my XP drops to a very low level. I need it set high but the default seems to be low. I often reset the slider.
I have tried changing the sliders in the volume controls, but they keep dropping.
Is there a way to change this permanently?