You mentioned you got a new graphics card.
Did you hook up the required 6 or 8 pin connectors to the card?
Can you current power supply handle it?
Besides not correctly installing drivers i can't think of anything else.
My theory is that Hydrophobia runs because the game isn't that graphic and the graphics card can stay in 2d mode which draws a lot less power than 3d mode that most other games would require.