With the release of version 0.8 yesterday, I have added Windows 7 as a supported operating system for Radio Downloader. I've also dropped support for Windows 2000 - this doesn't mean that I will block it from working on 2000, but I won't be routinely testing it on that OS from now on.
Radio Downloader works fine on Windows 7, but due to the updated behaviour of the system tray, the icon for Radio Downloader is not displayed when the main window is closed. A workaround for this is to right-click on the Radio Downloader icon in the taskbar when the main window is open and choose 'Pin this program to taskbar'. This will then keep the Radio Downloader icon on the taskbar when the window is closed, and can be used to re-open the window.
I've raised a number of bugs for improving integration with Windows 7 and the new taskbar, and I hope to address these over the next few releases.