Q1: I cannot install SQL Express 2008

You can download it here. If you have the following error:

Please follow the steps of this site to fix it: http://www.dotblogs.com.tw/ching/archive/2011/01/13/20777.aspx

Q2: SQL Express 2008 installation steps

Q3: I have problem using PORTimizer

You can try to uninstall SQL Server 2008(Express) and PORTimizer, and then install PORTimizer again.
More screen shot for Windows 8:

When you see these screens,
  1. Click "More info"
  2. Click "Run anyway"
  3. Click "Run the Program without getting help"