I got the following message form Alpari regarding an upgrade to MT4 (646). I assume this won't affect Zorro performance, right?. Though in my case I will have to upgrade to 646 since I am still runing in 509.

Dear trader,

This weekend we’re upgrading our MT4 live servers to the latest build of MT4 (build 646).

The latest build introduces several new features, including a dynamic built-in search function, MetaQuotes’ new books category, alerts and emails via MQL4 applications to popular email service providers such as Hotmail, and the ability to scale MQL4 dialog windows.

Will the update affect me?

Clients currently using build 600 or higher will not be affected, but we do recommend that you upgrade to the latest build for optimal MT4 performance.

If you are on a build lower than 600, you will need to take a few steps to ensure your Expert Advisors, indicators and other MT4 functions run as normal.

It would not affect you when your current MT4 version is 600 or above. Since it is older, you need to install the recent MT4 plugin as described in the manual. The folders and some MQ4 commands have changed in MT4 600.

MT 4 646 is giving some problem. After placing the zorro.ex4 and the key .dta file in Experts folder, and zorroMT4.dll and zorroMT4.ex4 in Libraries, and after clicking in Allow automated trading, DLL imports and external expert imports, it doesn't detect it. Even after reinitiating MT4 or trying to locate them in the metaquotes language editor to compile them.

The versión of MT4 646 I downloaded it from Metatrader.

There is no Zorro.ex4. An EA has the extension .mq4. Read the instructions in the manual. The first step is copying it in the right folder. Then it will appear in the Navigator and you can drag it to a chart.

In the MT4 509, the EA's are kept in the Experts folder as a MQL4 source files without extension and .ex4 files. This includes Zorro and the Moving Average default EA in Metatrader. There is also another file mqlcache.dat file. It may have extra meaning. I don't know. Like this, it has been working for long time, not only Zorro but many different EA's.

In the folder ZorroMT4 zip there is a Zorro MQL4 source file which I copied into the Experts folder of MT4 646 and in the Libraries there are two files, ZorroMT4.dll and zorroMT4.ex4, which I copied in the libraries folder of MT4 646. After reinitiating MT4 646 and clicking in the Allow automatic trading and allow dll imports and allow experts imports of MT4 646, it doesn't make zorro appear in the list of EA's in MT4 646. Am I forgeting something?

Well, finally I got some solution. I didn't took off the User Pannel Control (UAC), which I don't know if it had some effect in this issue or not, and I copied the files of Zorro in their corresponding folders but accessing them from the File Menu Open Data Folder of MT4 646. Like this, Zorrro comes into the Navigator.

MT4 646 has UAC always enabled unless explicitely disabled in the command line. So you normally must use the AppData folders as described in the manual. If UAC is disabled through the command line, then you must use the folders in the MT4 program folder.