Hello. WavesMaxx is a function of the manufacturer's audio driver -- in your case that means Realtek. You need to install a Realtek driver to get that feature. Dell only supplies a Win 7 Realtek for the XPS L501x. Try to install that driver using compatibility mode.
If that does not work then try a driver from the Realtek site. To get one direct from the Realtek site,
Go to the Realtek downloads selection page. http://www.realtek.com.tw/downloads/ On the page click on "High Definition Audio Codecs". Check "I accept" and then "next". In the column named "Description" find the file named README. That has the instructions for installing or updating. In the column named "Download", click on one of the server names to download the readme file. Go back to the column named "Description" and select your operating system (and whether it is 32bits or 64bits) from the top 2 choices in the list. In the column named "Download", click on one of the server names to download the driver.
Jim Coates -- 15 years on the Dell Laptop Audio boards -- since 2/6/04