What file can I alter to manually change the theme?

[N00b]

I know how to change themes using the config button on the site itself. However, I have installed and theme that apparently was not made for this version and instead it's crashed my site. I cannot get to anything on the site. Thus I cannot access the config section to change this. Can anyone please tell me where in the .php files I can go to manually enter the name of the theme I want to change to such as classic?

Thank you

[Casper]

Type this at the end of the url in the address bar;

Code Select Expand

?theme=classic

It should look like this,

Code Select Expand

http://www.mysite.com/coppermine/index.php?theme=classic

You will then go to your site in the classic theme, and be able to work your site again.