The game is running slowly even on a good system.

Heroes 5 is running very slowly: Lord of the Server. I set the lowest settings and played around with the extensions, but it doesn't help. The machine is well-suited for Heroes:
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2
System Manufacturer: WinFast
Processor: AMD Athlon(tm) 64 Processor 3000+, MMX, 3DNow, ~1.8GHz
Memory: 510MB RAM
Card name: ASUS Extreme AX550 Series
Display Memory: 256.0 MB
Current Mode: 1280 x 1024 (32 bit) (60Hz)
Brand: ASUS Model: ASUS Extreme AX550 Series, it seems like 512MB.
Resolution: 1024*768
Anti-aliasing and Anisotropic Filtering: on minimum.
Enhanced Image: off.
Detail Level: very low.

I had The King's Throne (may it be cursed), and everything runs on maximum settings there. It lags like this: for example, I'm riding a horse (elephant, dinosaur), I pass through 5-6 "points," and it slightly slows down. It's like I pass through, and then 0.5 seconds later, it "throws" me a little further (it's hard to explain). Or, for example, the Castle takes 8-12 seconds to load. Especially the Dwarves and the Academy are slow.
P.S.: I play all other games on maximum graphics or "heavy" games on medium settings. For example, Command & Conquer 3: Tiberium Wars
On maximum.