You can remove the Magento default callouts from either the left or right column copying the 2 files named left_col.phtml and right_col.phtml located in default/template/callouts to (your theme)/template/callouts
Then edit the two files and remove all content. If you haven’t a custom theme, just delete the content of the two files in the original position.
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*Here is another way I found that doesn’t involve deleting anything from the template files - BVBAccelerate*
1.Go to /app/design/frontend/default/(YourActiveTheme)/layout/catalog.xml
2.Find the lines that say <reference name=”left”> or <reference name=”right”>. In those there should be block definitions for the callouts.
3.Comment out anything that is a block you don’t want appearing
4.In the Magento Admin area go to System > Cache Management
5.Flush your cache
6.Reload your page in your browser