Any risk in creating partition after Windows is installed?

I am getting a new laptop with Windows 7 pre-installed. I would like to partition the hard drive so that Windows is installed on one and I can use the second as a backup/storage.

Is there any risk or anything I should be on the lookout for when creating the partition (like fragmented files)? Partitioning a hard drive is not new for me, although I normally do it when installing Windows for the first time.

Thanks.