Does Windows provide a unique identifier I could use to enforce a free trial?

Does the Windows operating system contains any unique computer/OS id?

This is for my own software. I want to create 30 day trial/demo version.

Here is what I want to do:

1. When someone installs a trial I grab the unique ID, send it to server.
2. After the 30 开发者_运维问答day trial, if software is reinstalled, the server blocks the trial version.

So the real question is: Does Windows contains any unique IDs I could rely on?

I think that IP address is not a reliable option.

Windows has a DigitalProductId. You can access its value in registry at the following location:

LocalMachine\SOFTWARE\Microsoft\Windows NT\CurrentVersion\DigitalProductId

I think widows key isn't enoungh: Windows 7 Family Pack - 3 licences for different computers at any one time; or any pirates, etc.

You could use NetworkAdapter's MAC instead. You can get MAC quite easy, here's an example in .NET: Read MAC Address from network adapter in .NET Sometimes computer can have 2 interfaces, so you could combine them into one key.