Manwe has given you a great answer to your question body (getting you back to a point where you should be able to access your SVN repository again).
I would go a step further and say that after you do that you should definitely give serious consideration to switching to git. You will have a working SVN repository, so you can use the tools that come with git to suck in the SVN repository and create a new git repo, and you have the
git-svnserver that comes with git that lets you emulate SVN if you have developers who can't make the move yet.
Among the advantages of moving to git:
Every developer has a full copy of the repository. They can commit locally and delay pushes if the server is down.
(So if you reinstall Windows and lose the server for a few days like what happened this time development can continue)
Every developer has a full copy of the repository. These are effectively a distributed backup.
(Don't rely on it as such, but in a crisis any checkout can be declared to be the "origin" repo).
git is just better than SVN
(OK, that last one is my opinion, but pretty much every developer I've worked with agrees -- Linus got version control right with git. It really is a pleasure to use once you get accustomed to the commands.)
Further reading on migrating from SVN to git: git ready: Converting from SVN.
Google will also throw out a plethora of results for
Converting from SVN to git or similar queries.
I also consider "A successful git branching model" to be required reading for people moving from CVS (and to a lesser extent SVN) -- Branches in git are a good (and painless) thing.