How to reinstall OS after replacing mother board?

Hi, I got my mother board replaced from Lenovo service centre. Now the Laptop is turning on and shows the options MENU to select any of the OS. "Earlier version or Win 7". But there is no reaction after selecting any of them .The service centre agent advised me to reinstall OS and check the Laptop. Now how do I reinstall or is there any other solution to dis and can I install XP first and recover my data which was earlier in the Win7 drive as I had dual OS from the beginning. I dont know about dual booting so I will I have to again create partition? or just simply install one by one both the OS. Please tell me in detailed steps the procedure to install. And I wont mind to get only Win7 installed coz I hardly ever used XP. Please Explain.