The Query Reporter use the Primary Oracle Home by default. This is the home that is listed first in the PATH environment variable.
To use a different home, you can change the PATH, or use the OracleHome command-line parameter. For example:
"C:\Program Files\QueryReporter" OracleHome=OraDb11g_home1
Note that this is the logical name of the home, and not a registry key name or directory name.