Unfortunately HOMAM 5 is a very intense game for any system due to some inefficient programming. It just runs slow with minimum system requirements and even a bunch of better systems.
Here's what you can do:
Update HOMAM 5 to the latest version.
Update your system/videocard drivers.
Run up to date antivirus/spyware.
Close all background applications.
Set the graphics settings in the HOMAM 5 menu to their lowest. Just mouse over each option and the game will tell you if it should be on or off for maximum performance.
It's all minor stuff, but it's all you can do besides upgrading your system.
PS:
http://www.gamebanshee.com/forums/mi...gic-series-99/ would have been a better place for this thread I think