Dear Sir or Madame,
I am writing to complain about computer, which I bought in your shop in Warszawa yesterday.
I feel dissapointed, because when I went to home this product didnt't work. I bought this computer for my children, now they are very sad. I checked everything in shop and it was all right. Now, when I turn on computer "OC fail, please enter to setup the change OC Fail settings" is displayed on the monitor. Additionaly, the screen goes off.
I will be appreciate if you repair this product. If it is not possible, I would be grateful if you could consider a full refund.
I am looking forward to hearing from you soon.
when I went home/got home/was at home
I will appreciate
przed 'computer' powstawiałabym 'the', about the computer, on the computer
literówka przy didn't