Cant import Terrain Assets

Hello, the first time i imported it i had no problem, but i deleted the folder “Terrain Assets” from the Assets folder but i need those trees. So i try to re-import it but it says “Decompressing” for some seconds and then Unity (4) closes and opens the report bug window. What can i do?

it might be that you have no memory or an out dated hard drive, disc drive

I finally used an other pack i found and it worked. I have plenty of memoryand drive. I Also have some tree prefabs with normal size, but when i want to use them with the tree tool they show up extremely small. How can i fix this?

I finally used an other pack i found and it worked. I have plenty of memoryand drive. I Also have some tree prefabs with normal size, but when i want to use them with the tree tool they show up extremely small. How can i fix this?