uploading movie files, changing file size

I have a few problems.
I have a .mov file I want to upload to an existing item page but its too large, approx. 38 mb. How can I change the code so that I am able to upload files that large?

I tried to upload the file to the dropbox, but I kept getting the same error message - Omeka Has Encountered an Error
To track the contents of this error, please enable error logging. Consult the Omeka codex for information on retrieving error messages.

I trie dto tackle this on my own and got nowhere. Please help...

Thank you in advance.

Is the /files folder in the Dropbox plugin writable (plugins/Dropbox/files/)?

Check the instructions in the codex for the plugin if you need help with this step: http://omeka.org/codex/Plugins/Dropbox

And if you wish to enable error logging, you can do so by following these instructions: http://omeka.org/codex/Retrieving_error_messages