can't replace windows 7 with ubuntu 12.04

view story

http://askubuntu.com – I have windows 7 and wanted top replace them with 12.04 but when I was booting and starting installation of ubuntu I chose replace windows in my ssd and it saw this problem. "/dev/sda contains GPT signatures, indicating that it has a GPT table. However,it does not have a valid fake msdos partition table, as it should. Perhaps it was corrupted-possibly by a program that doesn't understand GPT partition tables. Or perhaps you deleted the GPT table, and are now using an msdos partition table. Is this a GPT partition table?" Even when I click yes or no it does not move on it seem like a no (HowTos)