Hello I have a Fujitsu lifebook a series ah531. it came with windows 7 home premium operating system. My son decided to use my CD for windows 7 professional and now there is no way to activate that as it was installed on my Toshiba. the system recovery does not let it go back to original o/s. I do not have a cd to use. I do not know how to reformat the c drive because it wont let me says i am using windows 7 professional and it can not reformat it. Any idea would help getting that message from Microsoft to activate the windows 7 professional.