KNOW BEFORE INSTALLING TWO OPRATING SYSTEM (OS) ON ONE COMPUTER

ANSWER:-

• Remember that the two OSes should be same like it should be of windows series.or of Ubuntu or macOS etc.
• Do not install two OS of different companies like windows 7 with Ubuntu or vista/Xp with macOS etc.(this is because different companies programmes different BOOT manager,if you install two different OSes of two different companies then your computer's performance will be lowered and also it hangs several times and may result in hard drive burn sectors).
• Not to install the OS in same drive.its better to install two OS in separate drives.
• Make sure that the installing or installed Os file is not corrupted or missing.
• Regular updating of OS software will give user better performance.
• Sometimes due to Two installed windows computers hard drives sectors get brunt.out of 100 user only 5 user suffers from this type of problems.
• user can install the following OSes into there computer: 

windows 7 and vista.
windows 7 and XP.
windows 7 and 8.
windows 7 and server.

windows vista and XP.
windows vista and 8.
windows vista and server.
windows vista and 7.

windows XP and server.
windows XP and vista.
windows XP and 7.
windows XP and 8.

windows 8 and 7.
windows 8 and vista.
windows 8 and XP.
windows 8 and server.

UNIX with any UNIX version.
MAC with any MAC version.
UBUNTU with any UBUNTU version.
etc

thank you :)