Why does my server always redirect to localhost when I visit a subdirectory on the server?

System admins and Linux gurus, here’s one for you:

I’m a bit of a newbie at this. I installed nginx on a server that originally ran apache2. I tested out nginx and found that going to the server’s address worked fine, but whenever I went to http://serverip/folder it would redirect to http://localhost/folder and because I had nothing running on localhost, it would give me a 404 error.

I decided that I would try nginx at a later date and uninstalled it using apt-get—purge remove nginx and switched back to apache2.

When I started up apache2 I discovered that it had the same problem as well.

Yes, I have checked the hosts file on my machine, and on the server.

Yes, I made sure there was only one server daemon running at a time.

Yes, I have Googled it.

Can anybody help? I’m more than happy to provide my config files if you need them.