Here is the support site that's specific only to your
Dell Inspiron 1521 laptop.
You should add and save this site to your browser favorites/bookmarks list so you can refer to it when needed.
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Go into Control Panel - Device Manager, then click the + in
Sound Video And Game Controllers, then double-click the Sigmatel entry to open its properties window, then click Driver(tab).
What's listed for the driver version and driver date? If it's older than driver version 6.10.0.5609 and driver date 01/16/2008, you can download it from
here.
Download and save it, close all open windows first, then double-click the saved file to install it.
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Are the movies and video clips displaying okay and it's just a problem with static sound?
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That laptop came with only 1024 MB(1 GB) of RAM, but it supports up to 4096 MB(4 GB) of RAM.
Considering it's running Windows Vista(which is graphic-hungry and memory-hungry), you should really add another 1024 MB(1 GB) of RAM to it.
It uses 200-pin DDR2 PC2-5300 or DDR2 PC2-6400 SODIMM modules.
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