WordPress .htaccess file doesnt allow me to access other scripts

I was running TGP script in a sub directory. But since I installed wordpress on my root. I cant access TGP admin pages anymore. for example
request like “http://mydomain.com/st/admin/index.php” result in a 404 error page from wordpress.

I think its something to do with .htaccess file can you please tell me how I fix this thing.