2Gb (2X1Gb) Memory RAM Compatible with Dell Optiplex Gx520 Series Desktop By CMS A100 - Computer Memory Solutions
Best Buy: Dell Optiplex Desktop Computer 2 GB Memory 40 GB Hard Drive GX520
Upgrading Ram in the Dell Optiplex Gx520 - YouTube
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Dell Optiplex GX520 SFF: Front Source Tech
4GB kit (2GBx2) Upgrade for a Dell OptiPlex GX520 System (DDR2 PC2-6400, Non-ECC, ) at Amazon.com