I never download my pictures directly into My Pictures but use Corel Photopaint or Adobe Photoshop to see them on the camera (or take the card out and use a card reader in the USB port)
I then save them either as JPEF and/or BMP files.
If you take pictures with the camera on the RAW setting, make sure your graphics programme can read RAW files. They can be very large.
I am also assuming you have sufficient RAM on your motherboard.