How do I go about installing and managing data?

I have 2 hard disks.
1 old, one new. Both 7200 RPM. Both almost full, with 3 drives each.

Now my current Windows installation is on the new one but I want to put it on the old but both hard disks are full of data.

So how do I change this?

Normally, you'd make room on the old disk by moving some of the data elsewhere, or deleting some data.

Then make an image of the Windows partition(s) on the new disk, using a program such as Macrium Reflect.

Then restore that image file to the freed-up space on the old disk.

That's it briefly, but of course there are more detailed steps.

I'm assuming you don't want to do a clean install onto the old disk.

ignatzatsonic said:

Normally, you'd make room on the old disk by moving some of the data elsewhere, or deleting some data.

Then make an image of the Windows partition(s) on the new disk, using a program such as Macrium Reflect.

Then restore that image file to the freed-up space on the old disk.

That's it briefly, but of course there are more detailed steps.

I'm assuming you don't want to do a clean install onto the old disk.

So it's just basically all manual work, transferring data from here to there.
Yes, I want to clean install.