A thought experiment.  If I had physical access to a PC that was switched off, but I didn't know the password, could I boot into a live linux image and install software on the windows box?  Software like netcat for example
Install software to a windows PC through a linux live instance (e.g. Kali)
windows;kali linux
You have write access to the machine's hard disk, so you can add and modify files at will.Running an actual installer would be tough, but decompiling the installer and then manually doing all of its work (copying files and editing the registry) is possible. Another option is to run the installer on a clean VM, compare the before and after state of it (which will list all modifications made by the installer) and then replaying these modifications on your target system is also possible.From a security perspective though, malware usually doesn't come with an installer, it's either a single .exe that you put somewhere hidden and then add the corresponding registry entry to make it run at boot, or you completely replace critical system files with your own (malicious) ones.