If you've installed multiple operating systems on a PC then normally you'll have to choose the one you need each time from a boot menu.
Install Reboot-To and it'll add an icon to your system tray. If you need to reboot after that, right-click the icon, select Reboot > Operating System, choose one of your installed operating systems - Window Vista, Windows 7, Windows 8, Windows Server 2008 R2, Windows Server 2012, Ubuntu (wubi) and Ubuntu Server (wubi) are supported - and it'll reboot directly into that OS - the boot menu won't appear.
The change is just temporary. If you install and run Reboot-To on Windows 7, for instance, and reboot it to Windows 8, then the boot menu will only disappear for that one time. If you reboot Windows 8 as normal then the boot menu will return. (Unless you install and use Reboot-To there, as well.)
Reboot-To is a little more intrusive than we'd like, adding two background processes to our test PC: one for the user interface, another for a Windows service. These are extremely lightweight, generally consuming less than 2MB RAM on our test PC, but we're not entirely sure why they're required at all.
Allowing a program to play around with our system's BCD (Boot Configuration Data) files makes us a little queasy, too. It's carrying out a very simple and defined task, and there shouldn't be any problems, ever, but we'd still recommend that you have a Windows recovery disc to hand, just in case.
That aside, though, Reboot-To works very well, and if you're regularly booting between various Windows installations then it could save you some time and hassle.