Windows Explorer can be used to move files from the PC to a server using FTP. The images below were taken from Windows 7 - other versions of Windows may have a different layout for Windows Explorer.
Open Windows Explorer and ensure the Folders list is visible.
In the Address bar type:
ftp://email@example.com where username is the username for the site, and ftp.example.com is the ftp domain. (Some sites will work with www.example.com, some with example.com, some must have the ftp.example.com and some will be completely different.) Then click the "GoTo" button (right pointing arrow) or press the Enter key.
You will be prompted for the password. Then the files and folders in the web site will be shown.
Files and folders can now be browsed and dragged from the website to folders in the folder list. However, the reverse is not as easy - entire folders can be dragged from the folder list, but individual files can only be obtained by using a new instance of Windows Explorer, and dragging between the windows.