dual boot - If I resize a windows partition for install will that cause data loss?

I have a 40GB hard drive with 26GB free with a single partition with an ntfs file system that I want to install Ubuntu 14.04.2 on.

If I resize the windows partition for the installation, will the partition erase my data?

EDIT: The hard drive has no OS on it.

EDIT: Solved, I partitioned the hard-drive into two 20GB partitions and successfully installed Ubuntu without losing any data.

You'll only lose data if you shrink the partition too far. Use the Windows partitioning tools to shrink the partition a safe amount. Doing this manually with a such limited space is dangerous. How to do this:
Click on your start menu and type in "defragment". A tool for this will appear. Select it, and defragment your hard drive (this is to get the maximum amount of space). After that finishes, go to the start menu again, and type in "disk management" and choose the Disk Management tool. Right click on your largest partition (which should be C:), and choose "Shrink Partition". Windows will fill in a safe amount, but you can make it less. After it finishes, you will have more free space on your drive for Ubuntu.