Silverlight not only seems to be incompatible with (Microsoft's) SRP (Software Restriction Policies), but also allows DLLs to be downloaded and run without user's authorization. I'm using a non-Administrator account (LUA) on Windows XP Pro with full SRP - all programs and DLLs are restricted by default for LUAs. I download and install Silverlight (3.0.40818.0) separate from Netflix from a Windows Admin account. I go to the Netflix webpage and videos play fine from the Admin account. Go to my regular LUA account - get an "Error code 8151" when trying to play videos. Turns out by going to Netflix and playing a video, Silverlight has downloaded a DLL into my user area and run the DLL WITHOUT EVER PROMPTING ME that it was going to install executable code on my PC and RUN it! First, executable code should be installed into "Program Files", not under C:\Documents and Settings\<user>\Local Settings\Application Data\Microsoft\Silverlight\DRM\agdrm000.dll Second, since I never got a prompt saying it was going to download and install executable code, this seems like a major security hole (if the PC has Silverlight, simply download a Silverlight DLL with a virus, Silverlight will run the code). Third, the option to NOT "Enable download and updates to components required for protected content playback" (translation: install DLLs on your system from any website you visit without any prompting) is per-user, not per-system, so I don't see any reasonable way to manage Silverlight from an IT perspective. The "engineering" (if one can call it that) side of Silverlight looks like a total hack-job. If Silverlight needs addition DLLs, it should be a separate install to a system area, like "Program Files" (duh), and not the current hack, which creates opportunities for viruses, makes it difficult to lock down a PC against viruses (using Microsoft's own SRP), and makes managing software almost impossible (installing a DLL for every Windows user on a PC - you must be joking).