The most important information related to booting Windows OS will be in the Master Boot Record. This boot record enables the operating system to find the exact location of the OS startup files. Once this file gets corrupted you cannot boot your system until and unless your repair it or fix the problem. This issue will be often faced by those who usually use Windows and Linux or more than one operating systems. The reason behind this problem is simple; the master boot record of original OS is overwritten by the another OS. In other cases the file itself gets corrupted due to many possible reasons.
So I would suggest to take a backup of your Master boot record using HDHacker tool for your personal use to avoid such situation which might easily lead to loss of your important data. So if you want to be prudential and keep things safe then get a back up so that you can restore it whenever needed. This helps you to continue using multiple operating systems without any fear of loosing it. HD Hacker works fine for Vista, NT, 2000 and XP. So now you can backup the master boot record and restore it later when there is a problem. In fact even you can back up any other part of your hard disk like a sector.
You can select the drive using the letter or the physical drive itself. Read as well as write operations can be done using this tool. You can read or write only a sector alone if needed from a file or a disk and then have it written on to another disk or file. So when it comes to backing up the boot record which I was talking about you need to select the boot sector and later on write it to a file. So if this master boot record gets manipulated or corrupted or lost then recovery of the same will be easy for you.