Incompatibility between x86 and x64 in Installation solution

[rodnower]

Hello,

I have installation solution that have installer project (not web installer but simple installer) that installs NT services, web service and web sites with help of additional two projects of dlls with my own code that performs my installation step. In user actions of installer project I call installer function of one of those projects, and this project calls to installer of second project: installer -> MiddleCaller -> InstallationCore.

All this developing on Windows 7 and work fine when I compile all in 32 bit.

The project must run on Windows 2008. Because of some reasons all must be in x64 bit.

For this purpose, in MiddleCaller and InstallationCore I click right button of mouse on project -> build -> targer x64. For to move installer project to 64 bit in properties of installer (when project is active) I check: Target platform: x64.

When I run installation on x86 I get error:

The installation package is not supported by this processor type"

And this is good, because now I know that my installation compiled in 64 bit, but when I run this on windows 2008 I get:

Error 1001. Exception occured while initializing the instance:  
System.BadImageFormatException: could not load file or Assembly   
'MiddleCaller, v...' or one of its dependencies. An attempt was  
made to load a program with an incorrect format.  

Any one has some idea what I need to do for run fine the installation on x64?

May be I still not moved the installer project to x64 bit, if yes, where I do this?

Thank you for ahead.