Cant Boot from DVD and flash.

[Czech]

I have bought this Lenovo g780 laptop without an operating system, and I have tried, Installing Windows 7 of the USB and the whole process went well, but at the end when its done the computer keeps restarting, tried taking it out as I read in few similar topics, so I tried to instal windows 8 of tht same usb and tht worked fine and it even loaded in and I even worked with it for a while, but for my comfort id rather use windows 7 and I have this Windows 7 DvD tht i hv used recently on a diffrent laptop and tried to boot from it and it worked fine, but this laptop is just weird... I try to f12 boot from dvd and tht jst had no effect on it I tried to change the settings in bios and it still didnt answer to that... I dont know anymore what to do I tried to download diffrent Copys of WIndows 7 and it does exactly the same... so any1 any Ideas cuz I ran out of them, Id really apreciate some help to get me out of this very sadd situation, Thank you