Question regarding going from Windows 7 Prof Trial to the full version

I built a computer a couple months ago, and have been using Windows 7 Professional SP1 trial version (or evaluation period, whatever you want to call it). And I've decided I want to get the full thing of the same version. Like I would basically just like to unlock this trial version into full version. I'm not looking to upgrade to Ultimate or anything like that. I would like to keep what I have going now, but would just like to pay for the full version so I can continue using what I have.

Anyway how would I go about this? Would I need to buy a Windows 7 Professional SP1 Upgrade Disk? or a full disc of this version. And when I do buy something, I would only need a code right? since I'm using the same version I want to keep.>?

I'm just not sure how to go from Trial to Full of the same version. I see no need to reinstall anything right? I would just need to "unlock" it with a FULL VERSION key?

As you can tell I'm confused on what to look for to buy. Can someone point me in the right direction? THANKS IN ADVANCE>

There is no trial version of Win7. You installed a copy you haven't yet paid for.

If you have any qualifying XP or Vista retail copy on hand (which does not need to be installed) you can use Upgrade version key inserted at Computer>Properties activation link, after doing the quick workaround given in Option 3 of Clean Install with a Upgrade Windows 7 Version to activate upgrade version on a new or cleaned HD.

If you have no qualifying XP or Vista then you must buy a full version key. If this is too expensive you can install Windows 8 free preview version which performs as well or better than Win7 with a different GUI that can be modified to the normal Start Menu. Participating as a preview tester can earn you deeply discounted and free copies of the OS as it did us for Win7.

So if i want to go from my evaluation period Professional SP1 to the non-evaluation one of the same version, I would need to buy the retail Professional SP1 and input the key? With this method I would only need the key right?

Also, if I do that Windows 8 preview thing, will it erase all my files?

What does it say in your Computer Properties window as far as Windows being activated ?

If you made another partition to install W8 on, it wouldn`t wipe out anything. Windows 8 is not worth the effort, IMO.

Yes you can use the key for the same version to Activate at Computer>Properties, which is why I said so in my earlier post.

You can do an in-place Upgrade with Win8 which will keep all of your files, programs and settings in place, or download the ISO to boot it to Clean Install - back up your files first either way.
Windows 8 Release Preview - Download
Upgrade Install from Windows 7 or Vista to Windows 8
Create Bootable USB or DVD with Windows 8 Release Preview ISO