I am new to Linux and am excited to get started. However, I do not want to replace Windows 8, I would like to simply have two operating systems. I am installing from a flash drive. When I start my computer, I go into the BIOS, select SanDisk, select Install Ubuntu, and then it works. It does not, however, recognize my other OS and just wants to replace everything. Why is it doing this and how do I fix it?