No. It is the width of the tower case from left to right when the case is in its' standard normal upright position. The problem is the space available between the motherboard and the side panel.
The case you are looking at was introduced in 2006. It is an older model. New modern gaming cases are typically wider to accomodate 160mm tall tower style heatsinks.
You have two options. Get a wider case or consider installing a low profile cpu heatsink:http://www.frostytech.com/top5_lowprofile_heatsinks.cfm