|'i turned the computer of by unplugging it'|
Lesson learned...you can damage a motherboard by just unplugging the power cord. The safest way to shut down even if frozen is to hold in the power button UNTILL it shuts down safely.
You may have to use the option 'repair my computer' that comes up when you tap f8 at startup and then choose that.
You may have damaged your motherboard though.
Some HELP in posting on Computing.net plus free progs and instructions Cheers