You could purchase a "removable hard drive mounting kit" for about $20 and either purchase a new (standard) hard drive or use one you have laying around. This type of kit allows you to turn off the computer and easily insert/remove a standard hard drive. You can then save your images to this hard drive (either as partitions or files). When you're done, turn off the computer and remove the drive.
Note: You should check to make sure your system has the free physical resources to do this.