Hello Pacocha Jakub,
Thank you for posting in Q&A forum.
Based on the description, I understand you want to disjoin/remove/delete your machine (from your uncle) from your uncle's company, and then join this machine to your college organization.
Whether this machine is joined your uncle's company local Active Directory domain? If so, you can try to remove this machine from that domain, to remove machine from local AD domain, open System Properties (To rename this computer or change its domain or workgroup, click Change button).
If you can remove this machine from your uncle's company local Active Directory domain successfully, this machine account is still in your uncle's company local Active Directory domain (but the machine account is disabled). At this time, this machine will not be controlled by your uncle's company local Active Directory domain. You can join it to your college organization.
I hope the information above is helpful.
If you have any questions or concerns, please feel free to let us know.
Best Regards,
Daisy Zhou
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