For booting another legacy operating system from a GPT partition table the general advice is that you need a separate BIOS-BOOT-partition.For booting Linux in legacy mode on a GPT drive you need a BIOS-GRUB-partition without any filesystem and flagged as BIOS_GRUB.For booting UEFI you need a FAT32 EFI partition, one for each drive is sufficient and can handle several operating systems (this depends mostly on your UEFI firmware).Short answer: What Timur Fayzrakhmanov wrote is right, replace the /boot-partition with an EFI partition. So the questions are: Can I install Ubuntu 14.10 with only 4 parts: '/', '/boot', 'swap' and '/home'? What the partitions are odd here? (in the example above) I've read these two very helpful topics: efi-boot-partition-and-biosgrub-partition and how-to-use-manual-partitioning-during-installation.
I can successfully start Ubuntu by choosing 'boot from EFI file' option and specifying boot file at startup. However at the moment it doesn't matter, because my Ubuntu doesn't start, at the startup EFI says that 'no operation system have installed, please check the disk'. For now I've understand that is complicated task to use GPT and EFI on Windows 7.
The reason: after trying to install Windows 7 alongside Ubuntu, I enabled 'Legacy mode' on my HP pavilon laptop's BIOS (I think it is EFI, but it looks like traditional BIOS). I'm trying to understand how to properly partitioning the disk for future Ubuntu installations.