The situation is better now but i am not able to play the project with effects.

I will continue to 'repair' and optimize my laptop...

...or i should buy a mac book pro :-)

SuperG, for me the big DPC offenders on laptops tend to be...
- Battery (which can be disabled using Device Manager as long as you're recording plugged into the wall)
- Wifi - those Wifi radios use a lot of juice and when the start and stop pulling off the battery (trying to balance performance with power consumption) you get lots of DPC Latency. Just turn off your wifi card or disable it in Device Manager for the session.
- Video - this also is a battery hog and to increase battery life, the video drivers get kidna complex. You might try disabling the video driver in device manager. What this does is default to the standard video device driver from Windows that doesn't try so hard to be gentle on the battery.

I will try all these solution ti check the results...

If it does not work, i will install again the operating system...

Thanks!

Vagabondaggio,
 
Re-installing the Operating System is not likely to help you too much. Turning off things you don't need - identifying things causing problems (maybe your wifi card?) etc will be more of a help to you.
 
Reinstalling the OS when you're OS is working properly is not likely to help.

Ok, i will follow your suggestion. Thanks again...

I will follow most of the step. The situation is better but not enough.

Consider it as i wrote at the beginning.

If i open a New project, I can record several tracks without any drop out, with plugins in every tracks - i tried with 4-5 tracks.
After i save it and all it is ok.
When i open the same project, i can't do anything and it isn't able to play - not drop out, just only i push the play button and it doesn't start.
I have to bypass all the audio Fx to play it or record and i can't save - the message is 'out of memory' memoria insufficiente in italian...

I don't know what i have to do more...

Vagabondaggio,
 
One possible cause...
This can happen if your computer is scanning those new WAV files for viruses. After you finish your recording, the computer virus scanner will automatically start hunting for viruses in the new files. This uses a lot of resources on your computer while it is scanning.
 
If you leave your computer on for an hour and then hit play, does it play smoothly?
 
If so, you should suspect the virus scanner and disable it.

I disinstalled even avast anti-virus, turn off wire-less connection, closed every programs.
Now i have much less latency as i read in the report of LatencyMon...but it is not the solution...because cakewalk doesn't want to play the project with audio Fx...

Windows has it's own virus scanner in Windows 7+8. Hit the start button and type Virus Scan and you should find it. Turn that off.
 
If you have a laptop, try...
-- disable the batter in device manger (make sure you're plugged in first)
-- disable the video driver (these have power saving features)
-- disable the WIFI card
 
To do this, right click on My Computer and choose manage. Select Device Manager and then find these things within the device manger.