Deleting an SVN branch

Sure: svn rm the unwanted folder, and commit.

To avoid this situation in the future, I would follow the recommended layout for SVN projects:

• Put your code in the
  /someproject/trunk folder (or just
  /trunk if you want to put only one
  project in the repository)
• Created branches as /someproject/branches/somebranch
• Put tags under /someproject/tags

Now when you check out a working copy, be sure to check out only trunk or some individual branch. Don’t check everything out in one huge working copy containing all branches.¹

¹_{Unless you know what you’re doing, in which case you know how to create shallow working copies.}