Oh i get what you are saying. Well in my case it will be very suspicious if a user wants to switch computers very often so it's a good way for me. I will probably end up making a web form that will allow them to change their computers after a certain period of time. Then i will have them use an app that will generate the number for them and it will automatically put it in the clipboard so that all they have to do is click paste in the webform.
GUID
Free hosting is fine when you're not making a large scale website or anything that requires a big service load. Validation for a program that < 1000 people are going to use on a daily/weekly (opposed to hourly) basis isn't too bad. The problem is generally free hosting has unscheduled downtime and sub-standard support because you're not a paying customer. 000webhost periodically takes your whole site offline for hours at a time when it runs routine "safety tests" on your site to make sure there is no malicious crap stored on your account. So if your app is in high demand and can't perform validation because your host is down, you might find yourself losing users.
Look into HWID, or dont even do that do a Login system so the user has to supply user and pass on every login and lock the user and pass to the hwid..
UPDATE:
HWID can be found with GetCurrentHwProfile() function in the winapi. Just for those who weren't aware.
HWID can be found with GetCurrentHwProfile() function in the winapi. Just for those who weren't aware.

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