Please understand that I am not a Bootcamp expert, but here is what I suggest. First, look at what is on the disk you ate attempting to install. In other words, how large is the file to be installed? If it is a DMG (meaning compressed) you need to determine the size of the file after it is decompressed. Second, how much space you have available on the partition you are going to do the installation on? Can that be increased if necessary with Bootcamp? I ask because normally a partition can not be changed once created without erasing disk to do so.
Here is another idea to consider. If there is insufficient space available, maybe you could use an external disk (properly formatted) to install onto. I hope this helps and good luck.