Cannot find "Run Ubuntu alongside with windows" option when installing [duplicate]

How many partitions do you have. If you happen to have 4 primary partitions, then Ubuntu will say to replace your existing Windows since there are no more primary partition slots left (The maximum is 4 primary partitions).

Check to see if this is the case and decide which partition you wish to remove or change to a logical partition.

The explanation (With images) can be found in Is it possible to have Windows 8 and Ubuntu on the same hard drive?

The answer should give you an idea of how to remove one of the primary ones and create a logical one which can be extended to several partitions.