|We need to know more about your system. Model and specs.|
Is it a desktop or Laptop?
Was it a self build, an OEM supply (e.g. dell / Acer / HP, etc)
What kind of Licence (C.O.A>) is there on the PC?
What media did you use to Install? i.e. which flavour of OS?
We might then be able to offer some guidance.
Also please read for future reference:
☺ When everything else fails, read the instructions.