The simplest method seems to be calling SteamDecryptDataForThisMachine from the Steam.dll. You will also have to get the encrypted password from the clientregistry.blob (Luigi explains how to do this here:
steam-password-recovery-t488.html)... but once you do so, the code below works. Of course you'll have to re-write it in Delphi because it's written for AutoIT scripts, but it shows the basics.
Code:
$EncryptKey = "71627C0E720E06BE2060E6A209EFA434731B87103E330306611C93774800EF8E8D58A37AA603B06811FC5D714637"
$SteamPath = RegRead("HKEY_LOCAL_MACHINE\SOFTWARE\Valve\Steam", "InstallPath")
$steamdll = DLLOpen($SteamPath & "/Steam.dll")
$aCall = DllCall($steamdll, "int:cdecl", "SteamDecryptDataForThisMachine", _
"str", $EncryptKey, _
"int", StringLen($EncryptKey), _
"str", "", _
"int", 65535, _
"dword*", 0)
$FinalPassword = $aCall[3]
MsgBox(64, "Steam Login Info", $FinalPassword)
