Severance: Blade of Darkness is awesome! Everyone should try it out. As to the Heroes 3 i've played it so long time that im bored of it. I don't have anyone i could play with anyway.
EDIT: Those are games i recommend for weak graphic card:
Cortex Command (Pixel based game with awesome physics engine and many, many mods)
Gothic 2: Classic RPG (Warning: It may steal Your life though a bit buggy)
Severance: Blade of Darkness (Brilliant fight system, many levels and weapons)
Heroes 3: Don't need explanation
Worms: Armageddon (Though only for 2 players is fun)
Return fire: (Old-school great game as above for 2 players is the most fun)
Rally Championship Extreme: (Best rally game for me, decent graphics but really fun driving physics [I reccomend in-car camera only!])
Elastomania: 2d bike driving game with cool physics. Simple but addictive
Liero: Similar to Worms but with no turns (action!). Great for 2 players, and with map editor
Europa Universalis: Economy and strategic simulation of country.
Knights of Honor: As above. May be less gameplay options but still awesome game.
Total Annihilation: Classic RTS (Similar to Red Alert)
Thanks for the people who gave mi titles to some of this awesome games.