useing theme files from other dirs

Hi, i was wondering if it is possible to use theme files from other directories. I am building a website and would like to integrate the wordpress theme with the existing header and footer pages.

I already use @import for the stylesheets but i dont feel like reprogramming the wordpress theme files.

Also is there a way to allow wordpress to include files from other places using the <? include(); ?> because when i try it it gives me an error telling me that files cannot be included.

kind regards,