Question How safe? External clean SSD with Win 10 installed -> Plugged to laptop with infected HDD

[Pyrrho]

Could someone well-versed in software security explain to me "realistic" results of the following theoretical situation?

• I have a laptop with win 10 infected intentionally by an average programmer to steal user's data.

• I also have an external SSD with Win 10, installed and set-up on a clean/safe environment. This installation also contains bunch of non-malicious softwares...stuff like unity, mpchc, decoders, games & redists...

I plug the clean SSD with OS to the laptop with the infected drive. What happens?​

1. Is the infected hard drive essentially inactive, like a storage?
2. Since the new OS is running by it's own registry, would anything cause the infected software to run?

You probably see where I'm going with this even if I'm not proficient enough to explain it well.

 

[Tech Junky]

There's risk.
.
However since Windows is dumb to u can simply boot with a Linux boot disk and scan / remove the infection or just wipe the infected drive or use clonezilla to replace the infected install with your clean one.