Windows 7 Safe mode - Starting "Run Installer" and "Print Spooler" services

Windows Installer will not work under Safe Mode, this means that programs cannot be installed or uninstalled in safe mode without giving a specific command using msiexec in command prompt.

To make Windows Installer work under safe mode, you need to create a registry entry for every type of safe mode you are logged in to.

Run these commands from command line:

REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\MSIServer" /VE /T REG_SZ /F /D "Service"

net start msiserver 

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To Start Print Spooler
Method-1:

REG ADD HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\Spooler /VE /T REG_SZ /F /D Service

Net Start Spooler

Method-2:
Run Command prompt in administrator mode (right click and press "Run as Administrator"), and then run these commands.

Net stop spooler
sc config spooler depend= RPCSS
Net start spooler
exit

Reference:
1. http://www.symantec.com/connect/blogs/windows-installer-safe-mode
2. https://forums.techguy.org/threads/solved-enabling-print-spooler-in-safe-mode.1056317/
3. http://www.techsupportall.com/solved-print-spooler-error-1068-the-dependency-service-or-group-failed-to-start/

Activate/Enable Sound in Windows 7 Safemode

Here are the sequence of steps. For full steps refer the reference [1].

1. Run (Win key+R key) regedit
2. Press Ctrl+F
1. Make sure "Keys", "Values", and "Data" are all selected
2. Type in Sound, video and game controllers
3. Click [Find Next]
3. Take note of the branch address in the status bar at the bottom (it will be something like HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96C-E325-11CE-BFC1-09002BE10318})
4. Copy the device-driver GUID (the long numeric part between braces) and paste it somewhere like Notepad
5. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network
6. Create a new key (right-click, select New → Key)
1. Copy the GUID you saved and paste it into the key name
2. Edit the (Default) value and type Sound, video and game controllers
7. Create several new keys (under Network) called AudioEndpointBuilder, MMCSS and Audiosrv
8. Edit the (Default) values of each of the new keys and type Service
9. Reboot (you’ll boot into safe-mode)
10. Open the Services snap-in (Win key+R key → services.msc)
1. Search for "Multimedia Class Scheduler", "Windows Audio Endpoint Builder", and "Windows Audio Service services", and check if they are automatically turned on (they should be). If not start them. 

References:
1. http://superuser.com/questions/354325/how-to-enable-audio-in-safe-mode