Windows 10 apps not launching

I recently came across a problem with a new Windows 10 install where included apps (Calculator, Photos, etc) would not launch - at times even the Start Menu wasn't working. There are many possible solutions to this, though based on comments, many of them either don't work or even make the situation worse.

What worked for me was to check and fix permissions for the following:

In regedit.exe:
Right click on HKEY_Users and select Permissions...
Make sure that "All Application Packages" exists and has Read Permission.
Repeat for HKEY_CLASSES_ROOT

Expand HKEY_LOCAL_MACHINE. Check the subkeys HARDWARE, SAM,SOFTWARE,SYSTEM. Make sure that All Application Packages has the Read permission.

Other possible solutions are offered in this MS post.

Proxy script for blocking websites

This proxy script can be used in Windows to either block individual websites (blacklisting) or allow only specific websites (whitelisting), this example is for whitelisting:

function FindProxyForURL(url, host) {
 // Bypass the proxy for *.blogger.com
 if (dnsDomainIs(host, ".blogger.com")) {
               return "DIRECT";
 }
 return "PROXY http://127.0.0.1:18080";
 } // End of function

This is saved as a .pac file. In Control Panel, in the Internet Options, find the Connections tab, LAN settings. Uncheck “Automatically Detect Settings”. Click to check the box named “Use automatic configuration script”.

In the address field, type the location of .pac file as the following:

File://C:/Path/script.pac

More here.

Partly unnecessary Win7 services

A nice rundown of possibly unnecessary Win7 services, useful for slightly speeding up older computers.

Power shell script for Windows Server Backup status

Windows Server Backup does not include any notification possibilities - this script from Jocha.se is an easy way to add email notification via a custom task in Task Scheduler.

Computer last logon in Active Directory

A very useful way to check when a computer last logged on to Active Directory, done via PowerShell:

http://www.oxfordsbsguy.com/2014/04/28/powershell-get-adcomputer-to-retrieve-computer-last-logon-date-part-1/

Relevant commands:
Import-Module activedirectory
Get-ADComputer -Identity computer -Properties *

Command line tools for Group Policy

From Technet:

https://technet.microsoft.com/en-us/magazine/gg277500.aspx

Explanation of 3GB-not-4GB RAm problem

A post at MSDN for future reference.