Redondant uploads

Hi,

while backing up my blog (www.carsplusmovies.com) today, I noticed that all my uploads were being stored twice, both in the wp-content/ and in the wp-content/uploads folders.

The files in the wp-content/uploads folder have the name of the file corrected by WordPress (without capital letters), the files in the wp-content folder have the original name (with capitals) and sometimes a size in pixels (i.e 840x560x0) added as a prefix.

Is this normal? Could it be one of the plugins that I use?

Thanks a lot for your help,

Philippe