database connection could not be opened

Maybe its not the right place to post this, but I really need to solve this out.
I am having this Error " database connection could not be opened " when i try to install (AbleCommerce 7.0.7 )
 
Using:
- windows 7 pro
- IIS 6
- ASP.Net 4.0
- SQL Express 2005 / SQL Express 2005 SP3 / SQL Express 2008 R2
 
and this is my post on able-commerce forum " no answers until now " 
http://forums.ablecommerce.com/viewtopic.php?f=42&t=16113&start=0
 
Any one can help ?
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