Will this strategy to try Windows 10 work?

A friend wants to try out Windows 10 on a Windows 7 system. But they want the option to go back to exactly how things are now.

Their hard drive is 1TB (platter-based, not SSD), and they don't have a backup device that large.

So here's the plan:

1. Use Windows 7's integrated Disk Management to reduce the primary partition size to 600GB (the rest is empty space).


2. Create a Clonezilla live CD.



3. Use Clonezilla to backup that 600GB partition onto an external USB hard drive.


4. Switch their system from Windows 7 to Windows 10 using Windows Update.

We have run into the first snag: According to Disk Management, their hard drive has 3 partitions. The first is about 2GB and is listed as "Active, Recovery Partition". That makes sense, as it's likely the recovery partition from the system's manufacturer. The next partition is about 10GB and is listed just as "Primary Partition". The purpose of this partition is unclear; please see this question.

The final partition is listed as "Boot, Page File, Crash Dump, Primary Partition". This is obviously their Windows 7 partition.

Note that they have never installed any OS on their system except Windows 7, which came pre-installed from the manufacturer.

The questions:

1. Should this plan work?


2. In order to restore the system, will just having a backup of the last partition using Clonezilla be sufficient, or will there need to be backups of the other partitions as well?