This is my preferred method to scp files from a Windows machine.
Download PSCP from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Rename pscp.exe to scp.exe and place it somewhere in your PATH, like c:\windows\
Open a command prompt, type scp and then drag your file from an explorer window on top of the command prompt. Finish it out with your username@host:/path