Hello Techashar, If you are doing a clean installation only on Dirve C, the data on the Drive D, E, F should be safe. However, it is advised to back up all the data before re-installing the Windows. For more details, see How to Do a Clean Install of Windows Without Losing Your Files, Settings, and Tweaks. Hope this helps! 
 Suppose i have 4 partition of letter C,D,E,F. I have many important files in Drive D,E,F. My windows7 is located in Drive C. For information I only use Windows 7 in my laptop. Now if i make a clean installation of Windows in Drive C without doing any partition works, is my Drive D,E,F safe? Thank you.
About Partition