While preparing to move my boot drive to an SSD, I found that $PatchCache$ is over 3gb! I understand from reading that these are artifacts of updates and installs I have done over time and they should not be deleted. Can I move them to my slower E: drive and redirect via a mountpoint or some other method ?

Hello, You cannot be able to move $PatchCache$ to other drive. You can delete files under this directory if you want, and your applications will continue to run normally.DO NOT delete %WINDIR%\Installer no matter how large it might be. Leave %WINDIR%\Installer severely alone. I have found a work around for you:Click Start button, input “cmd” right-click command prompt and click run as Administrator.Type the following command to remove the Windows Installer baseline cache:rmdir /q /s %WINDIR%\Installer\$PatchCache$ You must stop the Windows Installer service for the change to take effect.You can set the MaxPatchCacheSize system policy to 0, so that the patch cache will not be created for this or any other products when patched. To see “Freeing additional space” of the article: http://blogs.msdn.com/heaths/archive/2009/08/09/atl-security-update-kb971092-still-offered-on-microsoft-update.aspxHope it will help you!