Microsoft SQL Server 2012 Requirements

During Microsoft SQL Server 2012 installation, in order to install SQL Server 2012 without a problem and an interreption please take care to the Microsoft SQL Server 2012 Requirements list.
It is better to install the Microsoft SQL Server 2012 requirements before starting MS SQL2011 installation or before you download SQL Server 2012 Denali Setup files.

The operating system requirements for Microsoft SQL Server 2012 is as follows.
Microsoft SQL Server 2011 aka SQL Server Denali CTP 1 Evaluation version supports :
Windows Vista with SP2,
Windows Server 2008 with SP2,
Windows 2008 R2, and
Windows 7 operating systems.
What is interesting related with the supported operating systems list is Windows XP is not supported any more.
Although I have successfully installed MS SQL Server 2008 R2 Developer Edition on my Windows XP PC, SQL Server 2012 Denali CTP 1 can not be installed.

It is not known that SQL Server 2012 CTP versions will work on Windows 8 beta, Windows Developer Preview release.

Here is a short list which you can review :
Windows PowerShell 2.0
Microsoft .NET Framework 3.5 SP1
Microsoft .NET Framework 4.0
Microsoft .NET Framework 4.0 Update (see details below)

Please note that this requirements for SQL Server Denali CTP may change with the new releases of Microsoft SQL Server 2012 and SQL Server Setup Application wizard.

Windows PowerShell 2.0 is an installation prerequisite for MS SQL Server 2012 setup. Windows PowerShell 2.0 is not being installed by the MS SQL Server Setup Application Wizard any more. If you are installing SQLServer on Windows Server 2008 R2 or Windows 7 operating system, Windows PowerShell 2.0 is already installed. But you have to install Windows PowerShell 2.0 manually on Windows Server 2008 or Windows Vista operating system running computers. Please download Windows Management Framework Core which is corresponding to your operating system from KB 968929 and install it for PowerShell 2.0
If you are not sure which version of Windows PowerShell is installed on your computer, please refer to guide How to Check Windows PowerShell Version Installed on a Computer.

.NET 3.5 SP1 is a requirement for MS SQL Server 2012.
Microsoft .NET Framework 3.5 SP1 is no longer installed by the Microsoft SQL Server Setup application wizard.

Microsoft .NET Framework 4.0 is also a MS SQL Server 2012 requirement.
But SQL Server 2011 Setup will install .NET 4.0 during the SQL Server features installation step.
Unfortunately, after .NET Framework 4.0 installation, SQL Server 2012 setup will require computer reboot.
In order to prevent SQL Server installed computer to restart after .NET 4.0 installation, an update installation which can be completed before SQL Server 2012 Setup will be enough.
Installing this update before SQL Server 2012 setup will prevent interruption during the installation process.

If you are installing Microsoft SQL Server 2012 (aka Denali or as expected SQL Server 2011) on Windows 7 or on Windows 2008 R2 OS computer or server, please download the .NET 4.0 update from KB Article 958488
If you are installing Microsoft SQL Server 2012 on Windows Vista SP2 or on Widows Server 2008 SP2 operating system, then please download Microsoft .NET Framework 4.0 update from KB Article 956250