Unless you take pictures from a well calibrated tri-pod position, you are bound to get some crooked pictures. It is advisable to straighten them for your viewing pleasure. This is especially so if you are going to print them!
Back to the previous post’s shot that was actually taken from a tripod but the engine bay was not going to always be nicely positioned and slight crookedness was found in the picture. This we viewed in Picasa.
The middle icon on the top row of icons is the straightening option.
Adjust using the slider bar on the bottom as necessary. Next … Auto-Contrast and Sharpening.