Limited access to Linux machines, need to copy files from Linux to a Windows PC

We have limited access to a client site, meaning we can't re-compile Linux kernels, install hard drives, etc.

We need to get a copy of user files from the Linux box(es) onto external USB hard drives. If USB is enabled on the Linux box(es) we might want to connect the USB drives straight to these boxes, but our fallback would be to copy the data to the USB drives attached to WIndows pc's.

My main question then, is, what is the best and most reliable way to copy files from Linux boxes to Windows PC's? I've been told we can connect to the network supporting these Linux box(es), so I assume some sort of FTP client, assuming the Linux box(es) are running FTP. I'm Linux challenged.

Please be detailed, with step by step guide as I will print the instructions to take on site.

Also, bear in mind that the Linux boxes are under the control of the SEC, and will be used as evidence. We cannot alter, dismantle, etc.

Thanks,

Michael Jackson