I just got a new laptop which of course is Vista 64-bit OS. When I went to install AutoCAD Architecture 2008, it said it could not be installed. So I searched the Autodesk Discussion Groups and found a discussion on this very topic. Below is an excerpt from that discussion that has what you need to do to get AutoCAD Architecture 2008 installed on 64-bit OS. It's amazing that I have not run into this until I actually tried to install it...I guess it just shows how many people are not using 64-bit OS's.
Note: These instructions use AutoCAD Architecture as the example, but can be used for AutoCAD MEP as well..
- Download and install Orca from Microsoft.
http://support.microsoft.com/kb/255905
- Copy the contents of the DVD to your hard drive or a network folder.
- Backup the files of the product .msi (ex: ACA.msi) and Setup.ini
- Edit the product .msi (ex: ACA.msi) with Orca and delete the action found in the table
"InstallExecuteSequence" that is called "CheckFor64BitOS" Delete the same
line under table "CustomAction" - Save and close the product .msi (ex: ACA.msi)
- Edit the Setup.ini with Notepad. Delete the line under
"#==================== Platform Requirement" that is labeled
"PLATFORM=NO_WOW_64_PROCESS" - Double-click the Setup.exe and you should be able to install without any
problems. - If you leave the default paths for the installation of the content, this may or may not apply.
- Some support paths under the "Files" tab of the configuration dialog box
have incorrect paths. The installer adds and extra "\AppData\AppData" to
some support paths located in the user profile. For example the Main
Customization File's path is listed as
"C:\Users\%username%\AppData\AppData\AppData\Roaming\Autodesk\ACD-A
2008\enu\Support\ADT" when it should be
"C:\Users\%username%\AppData\Roaming\Autodesk\ACD-A 2008\enu\Support\ADT"
- Fix the incorrect paths (if necessary), hit apply, and you are good to go.