Microsoft has released a security update for Windows 7, Windows 8.1 & Windows Vista.
Due to "security concerns", this intentionally disables the secdrv.sys driver -- a component of the SafeDisk protection which SC4 uses.
As a result, this prevents the disk-based (CD) version of SimCity 4 from running, and you may receive an "Access Denied - Please login with administrator privileges and try again" or similar permissions error. Many other legacy games are also affected.
It would seem the update simply disables the service, rather than removing secdrv.sys completely (like Windows 10 has).
NOTE: This shouldn't impact users of the digital game, such as from Amazon, Steam or Origin, as this doesn't rely on the same copy protection.
Full details of the update are as follows:
Security update for the graphics component in Windows
September 8, 2015 (KB3086255)
1) Purchase SC4 digitally
Online retailers such as Amazon, GOG, Steam, Origin or GamersGate offer a digital version of SC4 Deluxe.
This comes as a download without the need for the CD to start. It's also fully patched and doesn't use the same method of copy protection, so you can install KB3086255 without issue and play the game as normal. In the case of Amazon & GOG, the game is currently sold DRM free, meaning it starts by itself without a client service (e.g. Origin, Steam).
During seasonal sales, you can often purchase the game for as little as $5.
2) Redeem your SC4 Serial Number
You may be able to redeem your original Serial Number (product key), found at the back at the CD's manual. This may entitle you to a free digital copy of the game, with the same benefits of not needing other workarounds.
With Origin you can try contacting customer support, who can usually assist with this. As well as the serial number, you may need to provide physical evidence that you own the boxed copy, such as screenshots of the game's case & disks.
Other online retailers may also offer a similar option, so it's best to contact them directly.
NOTE: Use at your own risk!
The following suggestions will allow SimCity 4 to run, although they could potentially expose your system to security vulnerabilities (which the update intends to bypass). Therefore it's your own responsibility should any issues arise from not installing KB3086255, however the risk level of security flaws being exploited.
3) Uninstall KB3086255
If updates are set to install automatically, you may have this update already installed.
In which case, to allow the CD game to start again, without the need for any workarounds, you'll need to uninstall the update:
A quick way to check if it's installed:
Enter KB3086255 in the "Search Installed Updates" box at the top right.
Note: To reduce the risk, it might be worth disconnecting from the internet whilst the game is running. Also it's recommended to ensure your anti-virus has the latest protection definitions.
4) Hide KB3086255
If you haven't installed KB3086255, it might be worth hiding it from the list of updates:
5) Enable secdrv.sys on demand
However if you wish to retain the update, the below instructions (from the knowledge base article) describe how to start the service on demand, which should allow SC4 to run from the CD when you require:
Using a script
Alternatively, see the following link for a way to start the service using a batch file:
List of systems the update is offered to:
View the discussion topic in SC4 Bugs & Tech