I installed Windows 7 but the licence key apparently is wrong.
I installed from a downloaded ISO which, I guess, installed the highest version of Windows 7 (Ultimate) with a pirated key when I wanted to install with the key under the laptop.
Can I change the keys?
To change the key:
Control Panel\All Control Panel Items\System
And under Windows Activation choose Change Product Key
As in the following picture
I also found this: Downgrade: Change Windows 7 Ultimate to Premium or Professional if you are in fights with downgrading from Ultimate to Premium or Home.
But then on the other hand please refer to this question and answer.
While you can change the key, you cannot change the SKU (edition) of the windows installed. If you have a Professional key, you must install the Professional version of windows 7. If you download and installed from media containing Windows 7 Ultimate, then you will have to find another disk which will let you install Professional and use that to reinstall your system, and then activate it with your Windows 7 Professional key.
You should stay away from any installation media from unknown sources with unknown changes. An unmodified disc will not install without asking you for a license key, so you must be using a modified one. Using Windows installed from modified media can cause unexpeced behavior. Such media might also contain malware. You can download clean images from DigitalRiver, see How can I reinstall Windows 7 if I lost my installation DVD?
If you know your disc is unmodified by comparing the SHA-1 checksum withe the one published by Microsoft but it is the wrong edition, you can modify your image yourself to allow the installation of all editions using ei.cfg Removal Utility from http://code.kliu.org/misc/winisoutils/. Note, that the Windows 7 ISO Image Edition Switcher also available on that page is outdated and only works on discs without servicepack.
