I bought an HP laptop with windows 8 installed. For some reason I thought of installing windows 7. While installing windows 7 I got an error saying windows 7 cannot be installed to this disk as it's a GPT disk. So I thought of formatting my hard disk and changing it to MBR type. Accidently,I have deleted all partitions and now laptop is just blank. I tried using windows 7 installation USB pen drive to boot my laptop and tried using DISKPART to convert my GPT partiotion. But, It doesn't seems to be working. list disk does shows anything instead it just displays the name of commands and its use. Please help me. What should I do. I don't have windows 8 recovery disk or installation DVD.