Make sure the user has "admin" privileges before checking for updates, because it...

Make sure the user has "admin" privileges before checking for updates, because it's kind of pointless to download the update if you won't be able install it anyway. This is especially important for Windows XP, where we don't have UAC. Note that UAC implies "admin" privileges, because the installer process will be elevated as needed - even if the current user is *not* an administrator.