Hello!

I just found my old Spellforce Platinum DVD and was hopeing any of you could help me to get it run on Windows 8.1 64bit

Game installed just fine without any problems (Installed to C:\Games\Spellforce)

Specs that might matter:
CPU: i3 3127U
GPU: Intel HD4000 + AMD Radeon HD 7670M

You mean the game installed fine, but it won't run? No error message?
Try to install this - http://www.microsoft.com/en-us/download/details.aspx?id=8109 and run the game as admin (right-click shortcut/game .exe and select "Run as administrator").

No luck...
Game is patched to 1.52a
Direct X, Visual C and other crap are installed
running in XP mode
administration privileges
not working

This is the error I get when trying to launch... No error in 98/ME compatibility (though game doesn't launch in that either)
Problem signature:
Problem Event Name: APPCRASH
Application Name: SpellForce.exe
Application Version: 0.0.0.0
Application Timestamp: 000047d4
Fault Module Name: SpellForce.exe
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 000047d4
Exception Code: c0000005
Exception Offset: 00a04200
OS Version: 6.3.9600.2.0.0.256.48
Locale ID: 1061
Additional Information 1: 5861
Additional Information 2: 5861822e1919d7c014bbb064c64908b2
Additional Information 3: a10f
Additional Information 4: a10ff7d2bb2516fdc753f9c34fc3b069

Hmm, try using this installation guide - http://forum.spellforce.com/showpost.php?p=805116&postcount=6

Exception code c0000005 is a memory access violation. Unfortunately, only a crash dump to the developers will be able to tell you precisely what is causing it.