I installed Discoverer 220.127.116.11 on Windows 7 and it works fine.
To install it I had to go into Control Panel - User Accounts and set Change User Account Control Settings to 'Never Notify' then the install ran fine.
Then when running Disco Admin I had
ORA-12154: TNS:could not resolve the connect identifier specified
To fix this you need to create a Windows environment variable TNS_ADMIN that points to the directory where the correct Tnsnames.ora file is held.
On my system, I went to 'Computer - System Properties - Advanced - Environment Variables", created an environment variable TNS_ADMIN and set its value to C:\oraclexe\app\oracle\product\11.2.0\server\network\ADMIN
Check where your server or other tnsnames file is stored and set the corresponding value.
Then it all worked perfectly.