What's the word size of your Windows operating system, are you using a 32bit or 64bit operating system (sorry if I asked this information again, but I didn't find an answer in the threads above).
Let me get back to your listener.ora - can you comment save the current file in your gateway home\network\admin and create a new listener.ora file with only this content:
<space> (DESCRIPTION_LIST =
<space> (DESCRIPTION =
<space> (ADDRESS_LIST =
<space> (ADDRESS = (PROTOCOL = TCP)(HOST=localhost)(PORT = 1521))
and please make sure that you really have at least one <space> at the marked lines.
Then set again the environment variables and try to start the listener.
When it fails again, then please look into the directory C:\product\11.1.0\tg_2\network\trace - there should be a listener trace file. Best would be to upload it to a free file hoster like dropbox - posting it to the thread is also fine.
If you were able to start the listener above, then copy again the listener SID section to your listener.ora file and make sure to have also at least one space in front of the marked lines:
<space>(SID_NAME = SQLSERVER)
<space>(ORACLE_HOME = C:\product\11.1.0\tg_2)
My windows system is a 64 bit version - it could be the reason, are they compatybile?
I've done what you suggested and the "start" command fails again but in the "trace" folder no file has been created. I also tried after that use a Oracle Net Manager and I turned on logging and tracing right there but again during attempt of running start command no file in indicated folders has been created. I also tried to use a trace level "user" and "administrator".