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kel.7 - if you are still having problems
- if calibre (32bit and/or 64bit) appears in Control Panel->Programs and Features uninstall either or both;
- if present, delete the Program Files/Calibre2 and Program Files (X86)/Calibre2 folders, and contents;
- run a lightweight registry cleaner - here's some best free registry cleaner 2018 - watch out for extra bloat (e.g. CCleaner will offer Avast);
- If you not interested in previous calibre customisations/settings etc, delete the C:\Users\pjd10\AppData\Roaming\calibre folder.
If all else fails install Portable Calibre.
BR