The problem in directing you as to what to do and how to respond to what occurs when you do it is that because you are not knowledgeable about the computer you will have an almost impossible time understanding what we tell you and you also will not be able to answer the questions we ask you.
Is this computer still under warranty?
One thing you can try is if you can boot the computer to safe mode (start tapping F8 as soon as the computer is powered on) and then choose the option for "Safe Mode with Command Prompt" (with the up and down arrow keys), you can try a Windows System Restore, which will not cause you to loose data.
To start the System Restore tool at a command prompt:
1.Restart your computer, and then press F8 during the initial startup to start your computer in Safe Mode with a command prompt.
2.Log on to your computer with an administrator account or with an account that has administrator credentials.
3.Type the following command at a command prompt, and then press ENTER:
4.Follow the instructions that appear on the screen to restore your computer to an earlier state.http://support.microsoft.com/kb/304449/
This may or may not work, but if it doesn't work you have lost nothing.
Beyond that I recommend you take the computer to a qualified technician.