The Union of two partition hdd WITHOUT losing data, really?

Well, firstly, it is unclear how exactly are you going to build a section?
To increase the partition size regular means only if you have free space after this partition.
And the system partition which you delete as far as I understand in front of him.
Therefore increase will not work. (If the disk is not dynamic)

In General, the resizing operation does not damage the data.
But the slightest failure to execute the resizing - for example, will switch off suddenly, and all data will be lost.
Therefore, before operations on partitions, first check the availability of a fresh backup.

We have repeatedly faced with situations of data loss when manipulating partitions.

It is clear that in many cases, customers can keep back until the end do not understand what I was doing, but I would generally advise first zabekapit, then something to do.

Can including to create a disk image, in order to roll it back and have it all, including a system able to "exactly like now."

The hard drive ramping up extra space is not removed. Even the drive from which you need to take some space. Data is deleted only if you pressed delete or format.
For guarantee, can create a small disk to put data in there and build up.

Merged sections that were previously popular function in all programs for the control of drives/partitions, and file systems. One of the disks remains (main, boot or any other), the second is "poured" into it, becoming a folder on it. This of course, if you had to move with the data.
If you can remove all with the "second" (in your case the first) of the disc, that is no problem at all - delete the partition (that is, there will be Unallocated space), choose to rest - "extend" - this is done in literally ten seconds - a minute or two.
Here only the "back" 't remember if there are any features, like it shouldn't, but suddenly... Check on the virtual disk - create a VHD and it practice - to clarify.

If the trash is not greater than the volume of the system partition, it is possible after cleaning the system drive to move stuff there (as I understand it the first hard disk). Then remove the second disk and expand the first.
Well, backup is possible too.

If you have external storage that you can simply copy the stuff on it and work quietly with the disc.