I've seen Software has been installed many times on my machine.
Why do they use "been" with a past participle? They can simply say Software has installed.
Let's compare passive and active:
- In a passive clause expressing an action, the subject is not the agent of that action.
- In an active clause expressing an action, the subject is the agent of that action.
Now let's compare your two examples:
- Software has been installed.
- Software has installed.
In both cases, the subject is Software.
The clause has been installed is a passive clause in the present perfect (the combination of the present tense with the perfect aspect). This clause doesn't mark the subject Software as agent; instead, it marks the subject as playing a passive role. In other words, it's acted on another agent. You could say "The software has been installed by me", though you usually wouldn't.
In contrast, the clause has installed is an active clause. (It's still in the present perfect.) This clause marks Software as the agent; in other words, the subject is now playing an active role. It's not acted on by another agent, but assuming the verb install is transitive, it now acts as an agent on something else. When I see Software has installed, I ask myself, "The software has installed what?" This makes the sentence into nonsense.
However, the verb install is changing over time. Even though dictionaries mark it as transitive, a large number of speakers are beginning to use it as intransitive. As a result, Software has installed now sounds fine to many speakers, and many would consider it Standard English. It's still less common than Software has been installed, though, and I would avoid it simply because it doesn't sound as good to speakers for whom install is always transitive.
The PC says Software has been installed because it's the normal idiomatic English expression in this context, but Software has installed isn't.
It could be Software is installed, but that means something a bit different: it means that you are trying to install software that has already been installed. These days, because my PC has an unknown problem, whenever I try to access my online bank, I'm told that I need to install the latest JAVA update. So I download the update, click on install, and get the message "JAVA is already installed on this computer. Do you want to uninstall it?"
When Windows XP boots, it always says: Windows is starting up. That's got an unnecessary up at the end. I sent mental messages to Microsoft for ten years telling them about this problem. Somebody in Redmond must have received them, because Windows 7 says only Starting Windows. Maybe you can do the same thing to rectify the problem you see (but I doubt it).