SQL Query for Parent Child Relationship

I have db table with parent child relationship as:

NodeId    NodeName    ParentId
------------------------------
1         Node1       0
2         Node2       0
3         Node3       1
4         Node4       1
5         Node5       3
6         Node6       5
7         Node7       2

Here parentId = 0 means that it is a root level node. Now I want to write an SQL Query which will return child at all level of a parent category.

e.g. for nodeId = 1, it should return 3, 4, 5, 6.

I am using MS SQL Server 2005