Replaced by Newer Models

• The Pentax K10D was a high-end 10.2 MP DSLR model when it was released and was replaced by the 14.6 MP K20D. The Nikon D40 was an entry-level 6.1 MP DSLR model in its day and was replaced by the 10 MP D3000.
  
  

K10D is a High-End Model

• The Pentax K10D was originally a $1,000 camera that includes high-end features, such as weather sealing and an impressive continuous shooting mode. Also, 10.2 MP is the minimum a serious photographer would consider today. It is larger, heavier and of stronger build quality than the D40.
  
  

D40 is an Entry-Level Camera

• The D40 was originally a $600 camera that delivered good bank for the buck. 6.1 MP is high enough resolution to print photographs up to 8-by-10 inch, but no larger. It is smaller than the K10D, but not too small to grip comfortably.
  
  

A Word About Lenses

• As with any DSLR, you will spend more on lenses than the camera body. Pentax lenses tend to be cheaper even though they are of similar high quality to Nikon lenses. In addition, the K10D will accept older Pentax lenses from the film era, which can be inexpensively purchased on eBay or from local garage sales, although these lenses will usually require manual focus. As the image stabilization is located in the Pentax camera body, this is a huge advantage to going Pentax, as these high-quality older lenses will be image stabilized.
  
  

Other Cameras to Consider

• If you are leaning towards the entry-level D40, the Pentax K100D is a fairer comparison. If you like the higher-end features of the K10D, consider the Nikon D50 or D80.