Hi,
If you upload an image or other file then decide to edit the file and upload it again, you have to give it a new name.
I am using the File System "Common Instance" folder in Moodle 2.0 RC1 (Build: 20100927). I uploaded an image via FTP to repositories/FileSystem/images and used the File Picker to incert the image into a course. Then I decided to edited the image in Photoshop and uploaded it again via FTP to replaced the old version with the updated version using the same file name.
When I tried to incert the updated image into the course, the File Picker would not let me reselect the file. It said "ERROR, file already exists". It would not overwrite the file already stored in the database.
I had to rename the image file and using the File Picker select it and incert the updated image into the course under the new file name. That means that the OLD IMAGE FILE is still in the database taking up server space. There is no way to delete the old file.
I have reported this as a bug in the Tracker MDL-24410
Clarence