Merge data and operating system partitions

I have a hard drive to which I want to install Windows without losing the available files, so I used disk management on another PC to create 2 partitions, the first one contains the files, the other is unallocated. Of course the install should be on the last one and later remerge them.

What disk management gave me is the "data" partition to the left and the unallocated to the right, so the data one could be extended to the Windows but not the other way round.

Would that be possible, or the partition reserved to Windows should be on the left and therefore I should use some third party tool to move it to the left before installing Windows and then extend it?

The data partition should be on the right. Gparted if you need a partitioning program recommendation.