Installing SAP ERP 2005

Hi

I'm new to SAP R3 side. I'm a SAP Business One Consultant. I would like to know the following.

-To intsall SAP ERP 2005 (bare minimum with sales), what files must I download from the portal? We are using DB2 database and installing on Windows.

-In the portal where you download the software. There is rapid installer, and other links to go to install and upgrades. What is the difference? What is rapid installer?

-I know there is a version that works with MS SQL. But I only see db2 and oracle options for downloading?

-what is the bare requirements of hardware to setup test machine?

Thanks in advance.

Will reward generously 😉