I wanted to re-install Windows 7 and created a bootable USB (using command prompt I restarted my PC and selected primary boot device as USB-HDD (my BIOS also gives options USB-ZIP USB-CDROM and USB-FDD) but it went straight to usual boot. That it to dual boot screen. I thought maybe I chose wrong boot device in BIOS I tired all other options with no luck. Finally I formatted the USB and used Windows 7 USB DVD Download Tool to create a bootable USB. That have not fixed the issue.
I have one idea why I cant boot from flash. I have a dual boot (Win7/Ubuntu) on my machine. That could inter fear with PC`s booting process.
If you have any idea how to fix it or have meet similar problems please share your knowledge.