The ability to pick a file that's already on the portal site is one of the future enhancements that's been requested. Once that's done you'll be able to achieve what you're wanting to do.

There is a way to manually upload a file and 'attach' it to a repository record but it's manually intensive and VERY error prone .. so it's a high risk, but it's the only way right now with the current version of the module.

The problem is that the module inserts a GUID between the filename and the extension when uploading through the module, then strips out the GIUD when downloading. The only possible way to get around this is to upload a very small file with the exact same filename, then using FTP look for the file on the server and see what the stored filename (with GIUD) is. Then change the name of the large file to include the exact same GUID and FTP it up, replacing the small file. The filesize (calculated during upload) will be incorrect, so the last thing you'd have to do is manually correct the 'filesize' column in the grmRepositoryObjects table using a sql update query on the host tab, or sql enterprise manager.

Like I said, this is very error prone .. and although it *will* work, I would not recommend it unless you have no alternative.

I would suggest you spend your time fixing your environment so that you can upload via the module. Are your httprequest settings in your web.config sufficient? have you added the ExecutionTimeOut parameter to prevent yoru upload tasks from timeing out too soon? I have worked with people who are now uploading MP3 files that are 300MB+ in size without error.