There is no one answer to this question as it can vary depending on the specific computer and operating system used. However, in general, dual booting your existing computer with a different Linux or Windows operating system is always possible. However, it can be a bit more difficult than that and, often, you need to do some other tasks in order to achieve this goal.
One common method is to use a software installation program which combines the Linux or Windows installation process with the data and settings of the original computer. This can be helpful in ensuring that the computer is dual booted correctly from the beginning.
Alternatively, you could use a different computer with which you can dual boot. This is often more convenient for you as it can be used without taking care of the computer itself. For example, a car driver can dual boot with a different operating system on the left hand side and a different operating system on the right. This is often useful when you are driving and need to change or enter new settings without having to access the original computer.