How to get rid of dual boot

Sometime a unsuccessful system reinstallation or system upgrade will give your computer a redundant dual-boot.
Trying to get rid of dual boot could be tricky or dangerous. If you do something wrong, you won't be able to get into Windows again and all the data will be lost.
Actually Dual boot is fully controlled by a boot.ini file.
So everytime when you try to reinstall your system or update your system from XP home to XP Pro or any other system installation, all you need to do is backup boot.ini file.
1. go to startup menu,seclect MY computer and click the right mouse button, on the drop-down menu click "property" Tab.
2. From the "System Properties" windows, Click "Advance" Tab. Under "system Startup and Recovery" click "Settings".
3. Under "default operating System" Click Edit and then you'll be able to open Boot.ini in notepad. Then Save it on desktop or wherever you fancy.
If unfortunately you get a unwanted dual boot, what you need to do is just copy the original boot.ini back to the current boot.ini or compare those two and decide which system boot up you choose to stay.
Or if only if, you fucked up the boot.ini anyway and the system failed to boot up, what you're gonna do?
To see the solution, read the rest:
How to use Bootcfg command to edit boot.ini?
How to use use the Recovery Console to save your ass if you can't start up your system because you screwed up boot.ini(part 1)?
How to use use the Recovery Console to save your ass if you can't start up your system because you screwed up boot.ini(part 2)?