How to change picture with another one on a slide during slideshow? For example i put on pic of a car on the slide then i want to change it to a pic of a house after 2 second on the same slide during the show
And another question-how can i attach video file from my computer into a presentation and then to use this presentation on another computer where this video file doesn't exist?

You can do that with Animations. Animate the car with the Disappear animation and set it to start "After previous" which will be the slide being displayed, set it's duration to 2seconds. Then add the house and animate it with the Appear animation and set it to start With Previous and again with it a duration of 2 seconds or however long you want the house to be displayed.
Run slide show mode and test it out.
The car should appear on screen for 2 seconds and then disappear and then the house will immediately display.

If you want to use the PPT on another computer and you have video and audio etc linked I usually suggest you either have all files within the one folder and copy the whole folder to a USB OR use the Package for CD option which put all the files into one location and allow you to run it on another computer.

Hope this helps.

Thanks,it helped me