Something within WordPress is causing me validation errors

Hi,

When I enter submit search terms into the search bar on my site, and then put the resulting page through a validation test at http://validator.w3.org/check, I get the following validation errors:

Line 35, Column 200: cannot generate system identifier for general entity “feed”
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

Line 35, Column 200: general entity “feed” not defined and no default entity
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

Line 35, Column 204: reference not terminated by REFC delimiter
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

Line 35, Column 204: reference to external entity in attribute value
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

Line 35, Column 204: reference to entity “feed” for which no system identifier could be generated
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

Line 35, Column 199: entity was defined here
…ref=”http://www.projectdisobey.com/disobeyclothing/?s=Search+Term&feed=rss2″ />

I know that all these errors are resulting from an unencoded ampersand. My question is, which WordPress file do I need to go into in order to change the ‘&’ to a ‘& amp ;’?

Thanks