VERY GOOD NEWS !!!
I finally have been able to test California Megamod 3.0 in Windows 10 and it works perfect. I only had 2 small problems that was very easy to fix, and so i got it running perfect in just 1 minute. I'll tell you what i did step by step.
First I fixed a problem with Oracle VirtualBox in Windows 7 that didn't allow to work any version of virtualbox, it was the avira antivirus the cause of the problem, i went to hardware administrator, enabled Show hidden devices, and inside non plug and play drivers i found and disabled AVIPBB driver and now virtual box and avira antivirus can work together in peace (the second option was to uninstall avira and install AVG antivirus). So now with the virtualbox finally working again i can create virtual machines in my computer and install other operative systems and test the california Megamod, and try to solve any trouble that i find. The first test was Windows XP SP3 light and it worked fine as expected, this was to test that virtualbox was really working, and then i created another virtual machine to test Windows 10.
VIRTUAL MACHINE USED FOR THE TEST:
CPU: AMD A6-5400K at 3,60 Ghz (3600 Mhz) APU with RADEON HD 7540-D Graphics Core
RAM MEMORY: 3 Gigabytes (3129 MB)
GRAPHIC MEMORY: 128 MB
HARD DRIVE: 40 GB
OPERATIVE SYSTEM: WINDOWS 10 Professional 64 bits in spanish
GTA SAN ANDREAS RESOLUTION: 1024 x 768 x 32
I installed Windows 10 Professional 64 bits in spanish and activated it, while testing it i personalyzed some options in the menus, i disabled and/or uninstalled some useless things that i didn't want running in my PC, like the keylogger, and many spyware and addware. (you can click in the pictures to view them in full size)
Then i checked hardware administrator and i noticed that it had a very basic driver for graphics and this will not allow to run GTA San Andreas, probably. In order to enable 2D and 3D acceleration in the virtual machine i had to install Virtualbox Guest additions, in windows 7 and also in windows 10. It can be found in the oracle virtualbox website, very close to the virtualbox download links.
Now i started the virtual machine again and now in Hardware Administrator appears another driver from virtualbox and so i decided to try The Megamod. I only had installed Virtualbox Guest additions, nothing more.
Windows 10 already comes with a newer version of DirectX installed, so the game just needs 1 file that i already had included it when i released the megamod in january 1st.
So i got into the California Megamod Folder and found the folder named "USE THIS IF YOU HAVE WINDOWS 8"
Now everything is fixed and the game is ready to play. Please note that this fix works in windows 8, 8.1 and 10, and also in some Windows 7 that have the same problem, in others its not needed because the game works without this file.
The game loads and i set some settings in the options menu (graphic settings like Screen resolution to 1024x768x32, sound volume, language,...)
(you will notice that the megamod adds a new mods settings in the options of gta san andreas, you dont need to do anything in the mod menu, nothing to set there, so just leave it alone)
I start a new game. (sorry for the small screenshots from windows 10 the game is running at 1024x768, and when the game is running in windows 10 i can't use the screenshots taken from windows 10 because all i get is a black screen, so i must capture the screen from windows 7. you can click any image to view them in full size, they are taken at full HD, so you will be able to see all the detail from the windows 7 and windows 10 screens)
and the game starts normally, you can see CJ taking the bags in Los Angeles Airport, this is because STARMAN MOD allows you to play the original missions from GTA San Andreas, in other mods there are no missions and you start directly in the streets without cinematic sequences.
the game runs smooth and fast, even in a virtual machine. I only have a problem with the mouse been too sensitive but this is normal in virtualbox, it happens in any game, i can play fine if i leave the mouse alone and use just the keyboard, but i still have troubles to take screenshots because the mouse makes it difficult to point the camera where i want to.