I would like to read from PC a SD card that is inserted in a Arduino Wireless Shield.
So I don't want to remove the SD card from the shield, but I would like to read it simply by using a usb wire or wireless.
By wireless do you mean an ethernet WIFI card? You can use one of them to create an Arduino webserver website and and then build functionality to browse the SD card on the Arduino system from your PC via a web page including file upload and download (launch).
Have a look at my Arduino website at http://2wg.co.nz/. You can download the files in the PUBLIC folder but will not be able to upload files - you need to login for that.