Can I delete not loaded kext files?

I'm not sure what is being shown in the screenshot since there is no context, but I have to assume it is the "Extensions" folder within the "/Library" folder since I don't see any System extensions. If that is the case, then the items shown should be able to be removed, however, you have not provided us with the version of macOS involved here.

Ideally you should follow the developer's instructions for uninstalling their software. Only if that fails should you try manually deleting these items.

You should first boot into Safe Mode to ensure that these extensions are not loaded. Just because they are not loaded when you checked (not sure how you know they are unloaded), but a moment after checking their status those extensions could have been loaded & running.

While in Safe Mode, you should delete the associated .plist files for the software involved which may be located in any one or all three of the following locations:

/Library/LaunchAgents

/Library/LaunchDaemons

~/Library/LaunchAgents

You can then try deleting the extensions from the "/Library/Extensions" folder, but if they still cannot be deleted, then after deleting the corresponding .plist files from these folders, reboot the computer into Safe Mode. Now try deleting the relevant extensions from "/Library/Extensions" folder.

Keep in mind manually deleting these items is risky if you have more than one piece of software from that developer. You may end up deleting a critical component for another app from that developer since a developer may share pieces of software between their other apps.

FYI, you should always reference the exact version of macOS involved since it can be critical for many cases (knowing the exact model of the computer is many times needed as well although not for this particular case). It also helps to have a bit of background detail as well such as whether you tried following the developer's instructions for uninstalling their software, whether this software is really old & unsupported on this particular version of macOS, etc.

Plus when showing a screenshot of a folder, it really helps if we know the exact location of that folder.....I'm making an educated guess here. It is one of the reasons the regular forum contributors ask for users to post the full EtreCheck reports since it gives us many of the relevant details we need and saves playing 20 questions. Extra screenshots are Ok as well if it can help clarify things.

The short answer is yes. Yes you can.

You might want to provide some additional information though. For example, the fact a driver is unloaded does not mean it may not be required when a process depending on it expects it to be present. Should that occur, and the kernel extension is not present when the app or process requires it to load, it will not work correctly. Ideally, the app or process will present an informative dialog and shut itself down. Next best, the process will crash so macOS will shut it down on its behalf and provide a crash report. At the opposite, worst extreme, it will leave the system in an unstable state that may not be obvious or easily diagnosed. Unfortunately that is the most common result of using various and sundry "cleaning" apps that seem to be so popular.

Often the only symptom is that the Mac won't be working well — it becomes slow, buggy, apps crash or don't launch, fans blow and batteries die. Reinstalling macOS doesn't help, and the hapless user eventually gives up and buys a new Mac.

From the limited information shown in that screenshot it appears that a Western Digital "Drive Manager" or similarly ill-conceived utility was installed at one time, was uninstalled incompletely, or it remains installed affecting that system to some unknown extent. SDK 10.6 is over a decade and a half old.

You should run the third party app EtreCheck and post the complete report here so we can examine it. This will give us a better idea of the situation.

How to use the Add Text Feature When Posting an EtreCheck Report - Apple Community

The situation can also be a "No" if they happen to be old Kernel or System Extensions.....I know one of those two is no longer supported & have seen a few posts where they can no longer be removed depending on the version of macOS involved. The EtreCheck will help make things a bit more clear.

You're welcome. Thanks for the update.