Yes it is possible to install ALM 11 Starter Edition in an unsupported Windows Server 2008 64bit environment.
1) Use Setup.msi from the X:ALMInstallationWin64 directory
2) During the installation process, select to use the Evaluation License Key - Application Lifecycle Management instead of the Starter Edition license.
3) After the installation, login to the Site Administrator/ License tab then update the license with your Starter Edition License.
Another added benefit is that you can then use the Enterprice patches posted on the HP Support site instead of having to open an HP Support case each time you need a Starter Edition patch.