When installing Ubuntu (including Netbook Remix), if you have a lot of partitions on the disk, as I do for a variety of Linux installations, the disk partitioner window can be quite large. If you are installing on a netbook with limited screen resolution, such as the typical 1024x600, that window can be larger than the display area, and part of it will be off the right side. Unfortunately, it is that right edge of the window which contains the "Forward/Back" buttons you need to click.
To get around this problem, first, when installing Ubuntu on a netbook never choose the "Install Ubuntu...." option in the boot menu; this will bring up all windows full-screen, and you won't be able to move them around. Always choose "Try Ubuntu without changes...", and then start the installation from the desktop icon. Then, if you are installing the standard Ubuntu distribution, you can use Alt-Click-Drag to move the window when it is too large to fit on the display. But if you are installing the Netbook Remix, windows always come up full-screen by default, and thus can't be moved around. After you start the installation, you need to right-click on the title bar and choose "Unmaximize". You will then be able to use Alt-Click-Drag to move the window as necessary.