Numbered Steps to Reproduce Problem:
1. Uninstall a buggy (probably should have attempted to fix that bug rather than uninstalling, but I digress) BYOND using Windows 10 uninstall feature (Windows Settings > System > Apps and Features > Search for and select BYOND > Uninstall)
2. Attempt to reinstall the latest version of BYOND.
(These probably aren't the best steps, sorry.)
Code Snippet (if applicable) to Reproduce Problem:
N/A
Expected Results: I am taken through the installation process and BYOND is installed without any problems.
Actual Results: BYOND is unable to install, due to it apparently already running on my computer, which can't be right due to the fact that I have uninstalled BYOND. When I attempt to proceed with the installation I am unable to do anything but abort it.
Does the problem occur:
Every time? Or how often? Every time.
In other games? This applies to the BYOND installer so I guess every game?
In other user accounts? I have no other user accounts.
On other computers? I don't have another computer to test this on.
When does the problem NOT occur? It has always been occurring since I uninstalled BYOND and attempted to reinstall it. So I guess I'll just put a big fat N/A here.
Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)
N/A.
Workarounds: I have no clue.
In this case you uninstalled but you never shut down the BYOND instances that were previously running. If BYOND is still open in the background and not working, you have to close it via the tsak manager. Dream Deploy (and not the installer itself, which is an oddity) is trying to close it for you, but it can't because it doesn't have the right permissions; which means something on your system is much too locked down. So you'll have to close BYOND manually via the task manager. In the task manager's Details tab, look for byond.exe, dreamseeker.exe, dreamdaemon.exe, and possibly dreamdeploy.exe, and close any of those that you see.
I'd also like to address the freezing you mentioned above. It seems to me that if the pager were "completely frozen", you would not have been able to quit the application without using the task manager. I suspect what actually happened was that you saw a loading icon where the games list should go, which is a consequence of having either 1) a Japanese system locale, or 2) ASCII-unfriendly characters (accents, Cyrillic, etc.) in your BYOND user data path. The latter can be fixed by going to Pager | Preferences | Advanced and changing your user data path to some other directory that only contains basic English characters.