C# Signature:

[DllImport("rapi.dll", CharSet=CharSet.Unicode)]
public static extern uint CeRegOpenKeyEx(
    uint HKEY,
    string lpSubKey,
    int ulOptions,
    uint samDesired,
    out uint phkResult);

User-Defined Types:

uint HKEY_CLASSES_ROOT = 0x80000000;
uint HKEY_CURRENT_USER = 0x80000001;
uint HKEY_LOCAL_MACHINE = 0x80000002;
uint HKEY_USERS = 0x80000003;

Notes:

function info on msdn at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wceactsy/html/cerefCeRegOpenKeyExRAPI.asp

Tips & Tricks:

Please add some!

Sample Code:

uint key;
uint ret = CeRegOpenKeyEx(HKEY_CURRENT_USER,"Software\\TestApp\\Settings",0,0x1,out key);

Alternative Managed API: