Every file that you upload will count towards your disk space limit. You can upload as many files as you like until you reach this disk space limit. Each SiteMaker package has a different disk space limit which is easy to check.
Go to the toolbar and use 'Admin' –> 'Statistics' (advanced view) to see how much space you have used in total and how much you have left. Once you reach your limit you will not be able to upload any further files unless you delete some existing files to free up space in your account. Or you could upgrade to a package with a higher disk space limit.
For those using the 'basic view' to edit your site, you can check space usage in the 'Statistics' panel by using 'Edit' –> 'Manage your site', and then selecting 'Admin'.
Alternatively, you could upload your videos to one of many sites that host videos such as YouTube, Google Video, MySpace or Kewego. You can then link to this external video from a video player on your site and keep your disc space quota in tact.