Q: System-wide setting in Windows 7 and 8 - Registry is no longer useful? I want to track a setting system-wide on the target machine- it is a run time counter that keeps track of how many times my client runs my software. I decided to put this value in the registry, but I really want to track how many times it is run for the whole system, not just for the current user account. 
I would expect to use HKLM to track this at a machine level, but UAC doesn't like this nowdays. 
Is there a correct way to read and write a setting that is machine-wide?

A: HKLM isn't for this type of use (since Windows XP at least). 
Use the %PROGRAMDATA% folder instead (which you can also get via the WinAPI function SHGetKnownFolderPath with FOLDERID_ProgramData (SHGetFolderPath with CSIDL_APPDATA on Windows versions prior to Vista). It's specifically designed for application data that is global to all users of the machine. (On Windows 7, this is the C:\ProgramData folder by default.) Your application should create a directory beneath there and store the counter information in a file in that location instead.
(It also means you don't have to defeat the purpose of UAC by allowing public write access to the registry in inappropriate locations.)

A: From Environment.SpecialFolder Enumeration:
CommonApplicationData   The directory that serves as a common repository for application-specific data that is used by all users.
Have a "CommonApplicationData\Your Company Name\Your Product Name" folder created in your setup program and change the ACL for the folder to allow limited user full control permissions (the inherited permission is read only for limited users). You can do this via the LockPermissions MSI table, or if your setup program does not support LockPermissions, create a custom action to change the ACL.
You also need to handle potential edit conflicts created by fast user switching.
