This is really simple.
1. Create a "Content Webpart" somewhere on your SharePoint Page. If you want to hide it the moment the page loads, place it above your other content.
2. Add this code:
<style type="text/css">
.s4-recentchanges
{
display:none;
}
</style>
If you want to hide it for all pages
1. Go to "Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\Template\DocumentTemplates"
3. Search for the tag "SharePoint:RecentChangesMenu"
4. Add "visible=true" at the tags end.
If you hit save and reload the page, it won't show the "Recent Modified" menu anymore.