Problems deleting files from Sony A77

Hi All,

Recently got myself a Sony A77 and after taking some shots i went to view them on the computer. Now i wanted to delete a couple of folders but keep some of the others. I cannot seem to find a way to delete them on my computer. There is no option to 'delete'. the only way i can seem to do it is in camera, which is very time consuming and frustrating.

I have tried to find an option to alter the file properties and i initally thought that they were protected, but notihng i do seems to work. Please help.

Thanks,

LJM