hi can you please suggest me where i can online purchase the cabinet for my dell inspiron 1545 laptop

The focus of our site is on enterprise class datacenter solutions, servers, storage, virtualization, enterprise applications and the like. We typically don't have the best responses for consumer related questions. However, we have a sister site, the Dell Community that specializes in consumer related products. If you ask your question over there, you'll typically get a better and quicker response since you'll have more like minded eyeballs looking at your query.

The main site for the Dell Community is located here : http://en.community.dell.com/forums/

Specifically for your question, I would suggest you post it here : http://en.community.dell.com/forums/3516.aspx

Hope that helps !