As you have a Dell, for proper operation you need to use the Dell supplied driver
. I used to do a lot of support on the Dell forums and we found that non-Dell sound drivers
either did not work or did not work correctly.
Here is the Dell Vista sound driver, it will also work with Windows 7 as it is just "Vista improved". It is for both the 32 bit and 64 bit OS versions. Drivers and Downloads | Dell [United States]
This is a first step. If its still not working correctly after installing the driver, the next thing is what programs you are using that are "low"? If you click on the speaker icon in the notification area (lower right) you can set the system volume level.