it doesnt use winrar specifically, and I wouldn't use that for this
get 7zip
To be fair I use 7zip and I've had some compressed files decompress without the folder structure, so all the files are in the top folder.
What fixed that for me was double-clicking the compressed file, which should show you the top folder, right click that and "Copy", then create a new folder somewhere in your Documents, go into it and right click "Paste". It should decompress and copy the contents of the compressed file over to the new folder with the correct file structure.
But to be clear, I have no idea if that'll work for you, or why you're having a problem.