I've successfully set up NitroShare to send files between my Linux desktop and Windows7 laptop.

I'm now trying to go one better and set up a share on the desktop using Samba. That appears to have worked as I can see it in Linux file manager under Network. I can't see it on the laptop though. I have tried temporarily switching off the Linux and Windows firewalls.

Have you enabled network discovery and file sharing on the Windows 7 laptop? This is a good guide.

Turns out that the Linux end of it was straightforward, it was the Windows end that I couldn't get right . I get confused by all the different ways of doing things through the GUI, and I was using the name of the Linux computer instead of the IP address. I'm surprised I couldn't use the name though, as I saw it appear once or twice when I was trying to make NitroShare work.
Option-2 here explains how to do the Linux and Windows bits, the Windows part was what helped me.

Strangely, files which I put in the Linux directory via Windows have the padlock symbol but can be deleted.

Ain't it so true.

Then I guess the PadLock icon is for decoration,

You need to check the folder or file permission in Linux box. If it's 777 then I guess you need to fine tune the perms.

/etc/samba/smb.conf needs
To give the permissions I want to the copied files.