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I think you have misunderstood whatever you have been reading.
For the purpose of simplification, let us say there are two channels of Windows for distribution to consumers.
One retail and the other OEM(original equipment manufacturer).
For the first, support is supposedly supplied by Microsoft, since it has nothing to do with the people who sold you your PC or who built your PC.
The second, support is supposedly supplied by the people who sold/built your PC, since it was actually supplied with the PC.
Support in this case has nothing to do with updates etc, as both will be fully supported in that way equally. Support means that you can actually call Microsoft when you have problems.
This is where a lot of people get confused and begin making up all kind of stories of illegality and so forth.
OEM licences are cheaper because they are supposed to be supported by the people who built/sold you your PC. In this case, the OP has a Gigabyte PC with his Windows 7 being activated under the Gigabyte licence supplied by Microsoft. Gigabyte is expected to give support under this licence. So any upgrade is supposedly also supported under said licence. Of course we know that the PC is no longer under guarantee, so if there are problems with compatibility, a certain amount of self help may be required to find out if some component is not compatible. But the upgrade will be fully and legitimately licenced, even if it’s for free. But the licence stays with that PC.
The difference with the more expensive Retail channel is that the licence stays with the software. So you can uninstall it from one PC and install it to another ad infinitum.
I hope that makes it more clear.