My English is not very well,I am sorry.
It is an error's content.
Create new directory Temp failed.Please ensure there is enough disk and you have permissions setup correctly.
Unity 3d can be installed,and my C hardware can use space is 18.7GB.
When I try to change another save path or not,but object still can't be created.
My RAM is 2GB,so is OK right? I am not sure.