I'm trying to disable the warning message when connecting to a client - "The identity of the remote computer cannot be verified".
This is still WiP, I'm over it for today :)

Thought I'd record for reference the registry values the TS client (MSTSC v6.1 as with Vista) queries.
Lots of these aren't present by default. Many of these queries are also duplicated in HKLM but I've omitted these - we all know HKLM regedits are naughty :)

HKCU\Software\Microsoft\Terminal Server Client\DisablePrinterRedirection NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DisableClipboardRedirection NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\AuthenticationLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\AuthenticationLevelOverride NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\BitmapPersistCacheSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\BitmapPersistCache16Size NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\BitmapPersistCache24Size NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\BitmapPersistCache32Size NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\AllowUnsignedFiles NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\AllowSignedFiles NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\PinConnectionBar NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Default\RemoteDesktopFolder NAME NOT FOUND
HKCU\Software\Policies\Microsoft\Windows\CurrentVersion\Internet Settings\MBCSServername NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\EnableSslWithUserAuth NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Shadow Bitmap Enabled NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\UseShadowBitmapInFullScreen NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\MaxRdpCompressionLevel NAME NOT FOUND
RegOpenKey HKLM\SOFTWARE\Microsoft\Terminal Server Client\RedirectDevices NAME NOT FOUND
RegOpenKey HKLM\Software\Microsoft\Terminal Server Client\TransportExtensions SUCCESS
HKLM\SOFTWARE\Microsoft\Terminal Server Client\TransportExtensions\Gateway SUCCESS Type: REG_SZ, Length: 26, Data: aaclient.dll
HKCU\Software\Microsoft\Terminal Server Client\DisablePrinterRedirection NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DisableClipboardRedirection NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\AuthenticationLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\AuthenticationLevelOverride NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\PromptForCredsOnClient NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\AuthenticationLevelOverride NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\RemoteDesktop_SuppressWhenMinimized NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Min Send Interval NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Allow Background Input NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\OffscreenSupportLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\OffscreenCacheSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\OffscreenCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\BitmapPersistCacheLocation NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\MultiFragmentUpdateMaxSize NAME NOT FOUND
RegOpenKey HKCU\SOFTWARE\Microsoft\Terminal Server Client\Servers\<<hostname>>NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Default\AddIns\RDPDR\ThreadTimeOut NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\Default\AddIns\RDPDR\DisableDeviceRedirection NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\LicensingTimeout NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusEnabled NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusSupportLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusCacheLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusGraphicsCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusBrushCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusPenCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusGraphicsCacheChunkSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusBrushCacheChunkSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusPenCacheChunkSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageAttributesCacheChunkSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageCacheChunkSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageCacheTotalSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageCacheMaxSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawGdiplusImageattributesCacheEntries NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawNineGridSupportLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawNineGridEmulate NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawNineGridCacheSize NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\DrawNineGridCacheEntries NAME NOT FOUND
HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\AuthenticationLevel NAME NOT FOUND
HKCU\Software\Microsoft\Terminal Server Client\AuthenticationLevelOverride NAME NOT FOUND

Let me know if you find any of this useful and have further info on any entries.