Modifying your php.ini settings to the following will allow increased file upload limits:
upload_max_filesize = 50M
post_max_size = 50M
However, if you are using Internet Information Server (IIS), also check that there isn't a requestLimit set in the web.config. Drupal will show that a larger size is allowed via php.ini, but large files won't upload.
Here is the setting to change, on my system it defaulted to 10mbs:
<?xml version="1.0" encoding="UTF-8"?>
<requestLimits maxAllowedContentLength="10485760" />
Changed maxAllowedContentLength to 52428800 and 50mb uploads worked immediately.