Pictures Library is not a folder as such. Library is an index of locations of files. If you rightclick on one of the photos in the Pictures library and view properties it will tell you the actual location of the photo (should be your F: drive)
Get to know W7 Libraries click here
The Libraries feature in Windows 7 provides a central place to manage files that are located in multiple locations throughout your computer. Instead of clicking through a bunch of directories to find the files you need, including them in a library makes for quicker access.