Did you have PSoC Creator 4.2 installed on that PC before you uninstalled the PSoC Programmer? PSoC Creator 4.2 installs a newer version of PSoC Programmer than the one preset on the PSoC Programmer webpage at the moment.
If that was the case, since your uninstallation of PSoC Programmer is not clean (not sure what went wrong there), now you are seeing 'A newer version of program is already installed' error when you are trying to install slightly older version downloaded from web.
Please try reinstalling the PSoC Creator 4.2 on that PC. That should take care of PSoC Programmer installation as well. Make sure to remove all traces of PSoC Programmer from Programs and Feature and Program Files (x86) before you attempt reinstall the PSoC Creator 4.2.
The PSoC 4.2 installer now consistently crashes when it gets to the "PSoC Core" part of the installation. Is there any way to fix this so it finishes the installation?
I've tried installing PSoC Creator 4.1 and it now works, and the "PSoC Programmer not yet installed" error message is gone. However, I keep getting the "couldn't locate update manager" error, and I still cannot register my software.. Is there a fix for this?