Does anyone have any idea why the same email would be rendering differently in the same email client on different computers? A test email went out and was viewed on different computers, both on Windows and both in Outlook 2010.

In the the screenshot from Computer 1 below, the left column appears to be narrower, leaving more white space under the "Salem Stone" ad in the right column (as compared to the screenshot from Computer 2).

Could this be caused by a different monitor resolution? Has anyone else experienced this? I'm familiar with the general rendering differences between email clients and Mac vs PC, but this one is new to me. Any insight would be helpful!

Computer 1:
Computer 1

Computer 2:
Computer 2