While it's absolutely possible, usually you don't need to install both 32-bit and 64-bit versions of the application side-by-side.
Note, if you have both versions installed and you uninstall either 32-bit or 64-bit version, the counterpart becomes broken and won't start. To fix the problems, please use Repair feature as follows.
Go to Start-> Control Panel->Add/Remove Programs. In the Currently Installed Programs list, point to Softerra LDAP Administrator 2008 and click the Change button. Activate the Repair checkbox in the Application Management window and click Next. The re-installation of the application will correct this problem.