[support] User Uploads

Hello, In Drupal 5.9 what happens if two users upload files with the same name? I'm concerned that the second upload might overwrite the first. In my site there is a pretty good chance of this sort of thing happening. In my ideal world the file upload module would use sub-directories for each user, but it doesn't. If anyone can recommend a good module for file uploads, please let me know. Thanks. Daniel.