|I assume you mean your system disk is saying it is running out of space. |
Try disk cleanup. Right click C: properties
You could download Ccleaner & run that to clean up you disk.
What size is the disk?
If you have lots of large video files, all you need to do is copy them to you 1TB drive, then delete them from the C: (system) drive.
Post details of size of hard disk in pc. I assume My book is an external drive. You do not need any programs. You sound like you are new to pc's I would not recommend you use a partition manager.
A thank you would be nice, if I have helped.