Here's a search for articles on that: https://www.google.com/#q=screenshot+with+dropbox
Let me share that I did run into 2 PCs that hung like yours. Both had malware infections, one had Norton the other McAfee. So after a full backup image of the HDD was made since a lot of malware is now booby trapped we used Grif's advice at http://www.cnet.com/forums/discussions/how-to-remove-pup-option-603542/#post-f742c795-5881-433b-a29b-6d758efe5cd3 to remove the malware and finally uninstall the antivirus suites since those can interfere.
I'm not sure but suspect that CD/DVD drive emulators can interfere so those are remove along with torrent software.
So far that has fixed a few first hand and by reports from others, many others as well.
The key step is to have a full backup in case of a really nasty infection.
--> Almost forgot. Unplug things like printers, phones, scanners, USB memory/drives and such during such an upgrade.
several attempts to upgrade from win7, my download of win10 proceeds until after I sign accept then it sticks on the next window which is updates have left it on all night. HELP ! Microsoft have asked for a screenshot of the error. I do not know how to do it

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