Very Critical Problem

Solution
There can be several reasons for this.
Did you first partition and format the drive? Here's a link that shows you how to do it: http://wdc.custhelp.com/app/answers/detail/a_id/3865
Your HDD may be seen as dynamic drive instead of basic and that's why the Windows installation can't see it. So you might want to change that. You will also need to convert the drive to MBR partition, if it's not.
The reason can also be outdated drivers on your chipset so here's something from the Microsoft knowledge base that might help you as well:
http://windows.microsoft.com/en-us/windows7/windows-7-installation-problem-hard-drive-not-found
Also make sure the SATA controller is enabled and set ot ACHI.

Hope this helps you. :)
Keep us posted!
There can be several reasons for this.
Did you first partition and format the drive? Here's a link that shows you how to do it: http://wdc.custhelp.com/app/answers/detail/a_id/3865
Your HDD may be seen as dynamic drive instead of basic and that's why the Windows installation can't see it. So you might want to change that. You will also need to convert the drive to MBR partition, if it's not.
The reason can also be outdated drivers on your chipset so here's something from the Microsoft knowledge base that might help you as well:
http://windows.microsoft.com/en-us/windows7/windows-7-installation-problem-hard-drive-not-found
Also make sure the SATA controller is enabled and set ot ACHI.

Hope this helps you. :)
Keep us posted!
 
Solution