Always format in the camera.

According to Ed Ruf (REPLY to E-MAIL IN SIG!) <egruf_usenet2@cox.net>:

    I must admit that it sounds as though the program is editing the
images directly on the SD card, instead of copying them into the
computer and then working with them.

    I always copy all images from the card (CF for my D70, instead
of SD for your D50), and then work on the images with the card back in
the camera -- and formatted in the camera to flush away everything.  I
also actually copy to two disks to increase the chance of images
surviving a disk crash, and regularly back up on tape and DVD-ROM, and
always edit *copies* made for that purpose alone, leaving the original
images from the camera available for future modification starting from
what the camera provided.

    Yes -- if you are using small images and lower quality (higher
JPEG compression) it can get over the limit which the camera will allow
in a single folder, and automatically create additional folders.  I
never hit this limit with 1GB CF cards and fine/medium selected, but the
new 4GB CF card will allow me to hit this limit, even with Fine/Large
images, only RAW will not exceed the size limit.  (The limit is 999
images per directory.)  If you are not cleaning out the card each time
(ideally with a format in the camera), then you are likely to exceed the
size limit over time.

    I'm not sure about the D50, but with the D70, there is a
combination of two buttons (marked with red text) which when pressed
simultaneously will engage the in-camera format mode without having to
go into the menus.

    Good Luck,
        DoN.