Recursively searching the registry - windows

Question

I can successfully query for a known Key's value, using the code below. How can I recursively search the subkeys (in my example below, all subkeys within the Uninstall folder) for a particular data's value? My aim is to see if some particular program is installed, and if not, install it.
function
...(omitted)
var
Res : String;
begin
RegQueryStringValue(HKEY_LOCAL_MACHINE, 'SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\{92EA4162-10D1-418A-91E1-5A0453131A38}','DisplayName', Res);
if Res <> 'A Value' then
begin
// Successfully read the value
MsgBox('Success: ' + Res, mbInformation, MB_OK);
end
end;

Answer 1

The principle is easy, with the RegGetSubkeyNames you'll get an array of subkeys of a certain key and then you just iterate this array and query all the subkeys for the DisplayName value and compare the value (if any) with the searched one.
The following function shows the implementation. Note, that I've removed the Wow6432Node node from the path, so if you really need it, modify the UnistallKey constant in the code:
[Code]
const
UnistallKey = 'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall';
function IsAppInstalled(const DisplayName: string): Boolean;
var
S: string;
I: Integer;
SubKeys: TArrayOfString;
begin
Result := False;
if RegGetSubkeyNames(HKEY_LOCAL_MACHINE, UnistallKey, SubKeys) then
begin
for I := 0 to GetArrayLength(SubKeys) - 1 do
begin
if RegQueryStringValue(HKEY_LOCAL_MACHINE, UnistallKey + '\' + SubKeys[I],
'DisplayName', S) and (S = DisplayName) then
begin
Result := True;
Exit;
end;
end;
end
else
RaiseException('Opening the uninstall key failed!');
end;