Well, in that case you'll be needing to make the upload across several pages.
Do you have some way to split the file into pieces for uploading? (Obviously, the server can't do it because it's too big to get to the server!) *nix systems ought to have something like split lying around.
Have a form with a file upload field and a submit button. Choose the first piece and submit it. The form submits to itself.
If the script finds that it has been sent a file, give the file a unique name, save it somewhere temporary, and store the name of the file in an array. Store the array in a session variable.
Redisplay the form.
Every time the script finds that it's been sent another (piece of) file, it saves it with a unique name, and stores the name in the array.
If the file upload field is empty, this indicates that there are no more pieces to upload. If the script processes the form and finds that it hasn't been sent a file, it takes the filenames in the array, goes through the files listed there, reading them in one by one and writing them all back out to the same output file (which is the file you've been trying to put together all along).
The only bit missing is what to name the final resulting reassembled file. You could supply this in a text field, or it could just take the first name in the array.
