understanding resolution and pixels sizes

[pasknucklehead]

Hi again everyone,
Wow, talk about beginners, you're looking at one now.
I am having such a difficult time with uploading and enlarging and understanding how to make sure you have enough pixels to make a decent enlargement. I just took 50 shots of a friend and swore I had my camera, the d40 set to the largest size, 3000x2008 so I knew I could full well make enlargements should she want any. Well, I don't know what the heck I did wrong but I uploaded them to mpix, ( I love there work) and it is saying that my pictures can only be enlarged to a 4x6. I'm really freaking out here. I even checked back on my back up disk and it is saying that my photos are only 100x66 pixels. I don't know what I did. Can anyone tell me an easy way to figure out all this stuff. I know that I started out right by keeping my camera on the 3000x2008 but I don't know how they got reduced.
Thanks...
DC

[jerryph]

Picture resolution often has very little to do with PRINT resolution. A nice picture will be printed out in at least 300DPI on a printer to look good.

You likely over-cropped your pictures or saved them in a format of too low quality.

[reval8r]

You may have cropped the images and then changed the pixel resolution to a lower number which would make your pictures even smaller.

Make sure your print resolution is 300 dpi and your web images are 72 dpi.