Salesforce.com Dataloader for Sandbox

Scenario:

   You want to load data, update data through Salesforce.com Dataloader to the Sandbox Instance.

Solution:

1. Open up the Apex Dataloader tool.
2. Go to Settings==>Settings
3. Where it States Server Host (clear for Default) replace the https://login.salesforce.com with https://test.salesforce.com

See attach pic

Thanks
Ashok.