Here is an edited and corrected version of your story. I feel there were too many repetitious uses of the word "laptop" and I have tried to remove some of them without rewriting your own words too much. I have also changed several "could"s to "can"s because these are ongoing activities for you and "can" seems to work better. Apart from that, most of the problems are just in the phrasing and some spelling, and I have tried to improve the flow by linking some sentences together. I hope this helps you. My changes are in red.
Everyone must be have an important object in her or his life. It could be a souvenir, gift or book. However, the most important object to me is my laptop, a black Dell Inspiron with the model number PP39l. I bought my black laptop on August 2009 at Best Buy. It's rectangular in shape with a 15.6 inches screen and weighs 10 pounds. It has acted as a much needed friend, giving me a hand in everything that I do, like school homework, connecting with people and just relaxing.
Firstly, I really like the size of the screen because it is more comfortable for my eyes than a small screen when I have to do homework online. The laptop lets me browse websites online in order to complete academic assignments, check my email, and surf the internet to find study material.
Secondly, my laptop helps me connect with people. As an international student I missed my family and friends a lot after I went abroad alone. The laptop lets me chat with my family and other friends online. Sometimes, although my family and I are far apart we can talk and see each other by using the laptop camera. This is a convenient function that also saves me money. Moreover, I can visit Myspace and update my photos and the daily record of my life so my friends know what has happened in my life recently.
Thirdly, my laptop helps me to relax. When I'm stressed out by my school assignments or other trivial things, I can listen to music, read an interesting novel or catch up on the latest news.
To sum up, I could not live without my laptop and there is one experience that I will never forget. It was about two years ago, I went out with my friends and I left my laptop at home. Before I had left home my little sister asked if she could use it and promised she would not break it. I agreed to her request, but when I got home I could not open the laptop. I knew something had happened and no one was admitting to it, especially my little sister. I was really angry, but I could not do anything about it, so I sent the laptop back to the company. They took about fifteen days to repair it and I had nothing to do during those fifteen days; I could not surf the internet, read a novel, chat with my friends, check my email or even listen to music. It was all a real disaster for me. At least my sister eventually admitted that she had accidently poured a glass of water onto my laptop.
Therefore, the laptop is an important object for me. It is an electronic device with many uses such as providing study material, connecting with people and relaxing. The laptop is not only an electronic device, it's also a friend of mine .