Is Microsoft Windows GDPR compliant?

Windows 10 is GDPR complaint and moreover you can manage all your data collected by Microsoft at the new Microsoft Privacy Portal. 

There you can download all your data Microsoft has collected to-date. Download archive (JSON) file. If over >1G download this Liquid Studio Community editor for large files (Opens and edits TB+ files instantly, supports UTF-8, Unicode etc).

You can manage and clear your data for the following categories; 

1. Browsing history
2. Search history
3. Location activity - GPS like data
4. Voice activity  -  Cortana and other voice controlled services
5. Media activity - movies or TV data
6. Product and service activity - reliability and performance data to measure the quality of your experience
7. Cortana's Notebook - Notebook is where Cortana keeps track of your interests to give you a personalized experience.
8. Health activity - Microsoft Health, HealthVault, and devices like Microsoft Band can help you collect, understand, and manage your health data.

For an intro by Microsoft CEO Satya Nadella and an easily digestible introduction to all privacy concerns see https://privacy.microsoft.com/en-US/.