how to delete the url ?

I have a url http://www.xxx.com/keywords

This product is under the brand ABC

but a new url is auto coming http://www.xxx.com/keywords?manufacturer_id=13

you know this is a duplicate content , so I wnat delete...

where to change the url ?

which file I sholud modify?
Help Me Please.
Thanks

Hm ... I have the similar problem with products reached by Google by 2 categories AND a manifacturer. Although I use SEO friendly url google webmasters tools report duplicate content on the Title & Meta

Unfortunately I don't think that can be fixed

you will not a get a duplicate content penatly!

duplicate penatly does not work that way!

do research!