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Where do the 30-day trial versions of products (lets say Photoshop, for example) store the information that I've used 30 days up, or not? In the registry? In a folder dedicated to this? In a "secret" folder?

Not that I'm going to use this information for "evil" (forms evil plan), but I was curious. Will "cleaning" out my registry, using Piriform's CCleaner, for example, remove these "trial keys"?

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I'd figure many also register it in the cloud, but I don't know for a fact. Doing so, no matter how thorough you wipe your hard disk, your computer will still be known as being registered based on its installed hardware. Like Windows Product Activation. – Arjan Feb 11 '11 at 8:44
@Arjan What if you block it using your firewall? – Mateen Ulhaq Feb 12 '11 at 0:43
That totally depends. Windows won't activate then and nag you about it, eventually falling back to a limited version, for what I've read. Other software might not run at all, or run unlimited, I assume. Or might not update itself, which is a huge risk, especially for software that is used to open things your downloaded from the internet. (You wouldn't want to use an outdated PDF viewer or Flash player.) Another aside: you never know if unregistered software somehow advertises itself. Like Photoshop could add watermarks to files you create? (I'm not saying it does.) – Arjan Feb 12 '11 at 12:34
up vote 6 down vote accepted

It depends on the program. Please forgive my weasel words:

  • Some store the information in an encrypted area of the registry.

  • Some store the information in an encrypted file on your hard drive.

  • Some compile the date into the executable.

  • Some hide the info in an innocuous-looking file.

Your bigger challenge is that some of them don't store the date, per se, but number of times it was launched. And some will take note if you (for example) set your clock back to circumvent their checks.

In short, it depends.

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So, in theory, could there be a way to track these changes, and undo them? Check which files the program accesses, what changes it makes to its own executable (compare a copy of the executable you made before lanuch), etc? – Mateen Ulhaq Feb 11 '11 at 6:29
Yes, anything's possible (after all, that's how software cracking works), but if you get into the realm of reverse compiling code, and you're in the wrong jurisdiction, you could be breaking the law. – user3463 Feb 11 '11 at 7:09

This is up to the developer of the application, so it varies. Windows does not enforce how apps store their data. Some store it in the registry, others use the file system, others use alternate data streams, others embed it in a required EXE or DLL so if it's deleted the program won't run. Some even use multiple methods to make tampering more difficult. It is possible to hide registry keys from common tools like Regedit.exe by creating names that are too long or contain embedded nulls, or changing the data type.

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Alternate data streams, now there's something I didn't even consider. – user3463 Feb 11 '11 at 7:12

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