I apologize for the necro, but I've just come across this problem and the tool you've linked above is dead now.
Going into the registry editor, it is possible to fix the issue manually.
Open regedit, select "Computer" and then search for "paint.net"
Keep searching through until you find Paint.net, and delete the whole entry.
Continue through until you find a large string of text without the { }
Spoiler
For example, my entry was \Installer\Products\7AAD5202356081F46BF609E0F63202CE
Delete this entry
You should be able to install now NOTE: This is not advice. Only do this if you are one hundred percent sure of what you are doing.
Paint Net impossible to install
in Troubleshooting & Bug Reports
Posted
I apologize for the necro, but I've just come across this problem and the tool you've linked above is dead now.
Going into the registry editor, it is possible to fix the issue manually.
Open regedit, select "Computer" and then search for "paint.net"
Keep searching through until you find Paint.net, and delete the whole entry.
Continue through until you find a large string of text without the { }
For example, my entry was \Installer\Products\7AAD5202356081F46BF609E0F63202CE
Delete this entry
You should be able to install now
NOTE: This is not advice. Only do this if you are one hundred percent sure of what you are doing.