I have an Acer Aspire 7736Z-4088 with Dolby Home Theater Viritual SurroundSound. The operating system is Windows 7 Home Premium. When I try to turn the volume up louder I get a loud hum. The higher I try to turn up the volume the louder the hum gets. The computer has two volume settings: Realtek Digital Output (Realtek High Definition Audio) and Speakers (Realtek High Definition Audio). Each of the two settings have a range from 0% to 100%. I can only increase the Speaker (Realtek High Definition Audio) up to 46% before I start to get a loud hum. The higher I try to increase that setting above 46% the louder the hum. At the 46% level the speaker volume is not loug enough to hear DVDs very well.