There are 2 different ODBC Administrators on a Windows 7 64-bit machine.  The Administrator you are calling up is the 64-bit Administrator and the Pervasive ODBC Client Interface is a 32-bit driver.  You can find the 32-bit Administrator in c:\windows\sysWOW64.  You may just want to create a shortcut on your desktop that looks at the following:

 c:\windows\sysWOW64\odbcad32.exe 

This is the 32-bit ODBC Administrator.  If you run the ODBC Administrator from there you should see the Pervasive ODBC Client Interface as an option.