The .NET 4.0 and 4.5 install packages should contain both 64 and 32 bits in the same package. If you're unsure use the Web installer and it will install what's not already on the machine...

I would highly suggest you make sure your Web app compiles to 32 bit if you're using COM objects, since they are almost guaranteed to be 32 bit and will crash in 64 bit if they are.

To check what's really installed look in these folders:

C:\Windows\Microsoft.NET\Framework
C:\Windows\Microsoft.NET\Framework64

.NET 4.5 shows as .NET 4.0 but the build number will be v4.0.30319...

If any project in your app uses .NET 4.5 your will have to run in .NET 4.5, so make sure you don't have one project set to 4.5 on your dev setup.

+++ Rick ---

>I am having a problem running my Web sites under Windows 7 64 bits since I moved to VS 2012. I have:
>
>"Could not load file or assembly 'Framework' or one of its dependencies. An attempt was made to load a program with an incorrect format."
>
>It seems something in VS 2012 does not like the way I set up my references in my framework. I have found this link:
>
>http://www.microsoft.com/en-us/download/details.aspx?id=6523
>
>There is a mention about downloading "Microsoft .NET Framework Version 2.0 Redistributable Package (x64)".
>
>In my program files, I have the related ones:
>
>Microsoft .NET Framework 4 Multi-Targeting Pack
>Microsoft .NET Framework 4.5
>Microsoft .NET Framework 4.5 Multi-Targeting Pack
>Microsoft .NET Framework 4.5 SDK
>
>I am able to compile and run my applications on Windows Server 2003. But, I cannot on Windows 7 64 bits.
>
>Can someone confirm me if I really have to follow that link for the .NET Redistributable Package (x64) in order to be able to run my applications under Windows 7 64 bits, since I moved to VS 2012? Like I said, this was running before. But, VS 2012 seems to have changed something forcing something to be adjusted.