VS 2010 comes with MVC 2, but it’s not a part of the .NET Framework proper. This means that if you go download the .NET Framework 4 redistributable, it will not include the MVC 2 runtime.
But since MVC is bin-deployable, this is fine. Your application – when deployed to a .NET 3.5 SP1 or .NET 4 server – will just copy System.Web.Mvc.dll to its /bin folder, and everything will run as expected. MVC runs just fine in Medium Trust.
To do a server wide install you need to download AspNetMVC2_VS2008.exe from here, rename the .exe to .zip and inside the mvcruntime sub-folder you’ll find the AspNetMVC2.msi file.
Then you have to run:
msiexec /i AspNetMVC2.msi /l*v .\mvc.log MVC_SERVER_INSTALL="YES"