Can you upgrade any PC to a dual boot?

Does a computer have to meet certain conditions to use it as a dual boot?

For example, I want to use Kali Linux and Windows on my laptop.

I would not be aware of any conditions to set up dual boot except the minimum system requirements of Kali Linux. You can also easily set up Kali in a VM or with WSL.

Is Kali your first Linux?

If so, then first install another Linux distribution to familiarize yourself with the operating system. Mint or Ubuntu, for example, would be recommended.

Already in 1998 I installed dual and multiboot environments with XFDISK with Windows 98 and three Linux systems (Suse, Debian and Red Hat).

So today you can also set up 9-year-old computers with Windows and Linux. Windows 10 doesn't run that well on a Core 2 Duo with 4 GB of RAM, but it depends on your purposes.

This works out. All you need is hard drive space. Most Linuxdistris can "shrink" the Windows partitions if there's space on it and use the cleared space.

Since Win7 Windows can also "multiboot", so you are no longer dependent on the Linux boot manager. However, it is easier to let the Linux Distri provide the boot manager and, above all, to let the Distri set it up.

For a clean separation and to leave the Windows storage space completely alone, it is better to install a new hard disk. You can get an SSD with a usable size from € 30 and you can then install your Linux on it completely independently.

Tip:

If you want to be able to undo that, then take the new disk first in the boot sequence and install Linux, then the Windows boot manager remains unaffected. If you remove the new disk or switch the boot sequence back, the PC starts Windows exactly as before.