Windows 10: New files in C: drive

I only have my C: drive, because I have a laptop.

Today a couple random folders and files popped up in my C drive:

-mono.msi file

-System64 folder

-System folder

-Mono folder

I have literally never seen these before and didn't know they existed. I'm wondering what triggers these to appear, if it's a problem, and if so, how to get rid of them.

:)

 

C: Drive disk cleanup

I've already done your suggestions....... yep, need a bigger drive for C: suppose!

 

Installing Windows on my new C drive

Current Situation: My C Disk is cramming up and I decided to change a new C disk.

Currently my computer storage is composed of an SSD (being my C disk) and an HDD. I bought a new SSD and desire to somehow transfer my current system into the new SSD along with the current environmental variables, user data, both program files folder, and
various other folders instead of installing a brand new system on my new C drive.

Questions I am currently wondering:

1. I noticed the function provided by windows called "Create a system image". Currently my softwares are distributed evenly in my C drive (SSD) and D drive (HDD). I am not changing my HDD, so softwares installed there will not be removed. If I only choose
   to backup my system in my C drive, can I still run my softwares on my HDD after changing a C drive and reinstalling Windows using the generated ISO file?
2. Does this function "create a system image" pack up the environmental variables, registry, along with all other folders in my C drive, or only the minimal system?
3. If I extract the system image ISO into my new C drive, can I somehow "extract" from the ISO file to create a new system in my new drive? If not, is it possible to make my new C drive a windows Boot USB, and directly installing the windows system onto itself?
4. What is your suggested method of making this move?

Thank you for your help!!

 

Unallocated Space to C Drive

Thanks