hello and good afternoon. when I record I want to hear the music and my voice in the headphones. what can I do? I have windows 7 premium and audacity 2.0.7. thanks for your help and have a nice day.
Edgardo. 
I am very sorry but I can not find the answer to my question. also I have made a mistake because I wrote audacity 2.0.7 and is 2.0.5.
I apologize for this mistake. thanks a lot for your help. greetings.
edgardo. 
Turn both Transport > Overdub and Transport > Software Playthrough on (both checked).
See these FAQ’s:
http://manual.audacityteam.org/o/man/faq_recording_how_to_s.html#overdub
http://manual.audacityteam.org/o/man/faq_recording_troubleshooting.html#playthrough .
You probably won’t like it if you are using the built-in sound card, because unless you can unmute playback of your microphone in Windows you will hear yourself late, due to latency. You may want to turn Software Playthrough off and listen to yourself acoustically with one headphone off. See: http://wiki.audacityteam.org/wiki/Overdubbing_using_your_computer’s_on-board_sound_card .
Or do you have an external sound card?
What version of Windows are you on?
The more information you give, the better answer we can give.
Gale
as i said in my first post i have windows 7 premium 64bits and audacity 2.0.5 and i don’t have external sound card. thanks again for your patience and your help. greetings.
edgardo.
i have follow your indications and i have fix the problem. thanks a lot for your help and have a excelent weekend. greetings.
edgardo. 
Sorry, that was what I meant (64-bit or 32-bit). Your sound device must have 64-bit drivers to function correctly - see http://wiki.audacityteam.org/wiki/Updating_Sound_Device_Drivers .
I’m glad you have found an acceptable solution.
If you do overdubs a lot, and cannot unmute the microphone, it may be worth buying an external recording interface like some that Behringer make. You can then monitor while recording without any delay by using the headphones port on the interface and setting the interface to be the Audacity playback and recording device.
Gale