Trouble dual-booting Ubuntu and Windows 7

[vsporeddy]

This Lenovo G505s laptop came installed with Windows 8. I tried formatting that partition and installing Windows 7 x64 with a DVD but it wouldn't work because the disk is GPT. However, Ubuntu installed and worked perfectly fine.

But I wanted Windows 7 so I converted the disk to MBR in Gparted, wiping everything, and made 2 partitions. On one I installed W7, and it is booting fine. On the other I installed Ubuntu, and it worked fine from the LiveCD, but after restarting it just shows a blank dark purple screen. The GRUB menu is working and I can choose Windows or Ubuntu.

Things I have tried:
adding nomodeset in the grub config
trying all combinations of legacy/EFI boot options in the BIOS
running boot-repair from the LiveCD

Nothing worked. I'm sure the problem has something to do with either the graphics (this laptop has a weird AMD dual graphics thing) or some mismatch with EFI/BIOS booting. Any advice?

[fantab]

To install Windows7 on GPT disk you need to follow this tutorial (http://www.sevenforums.com/tutorials/186875-uefi-unified-extensible-firmware-interface-install-windows-7-a.html).

You must Reformat your HDD as GPT, install Windows7 and install Ubuntu.

MBR is outdated, no need to go back to it. Stick with GPT and UEFI.

GPT stores a backup of itself on the HDD. When HDD is converted to MBR this backup table is still present and this confuses the installer.
You can also remove the backup table with fixparts (http://www.rodsbooks.com/fixparts/) and continue to use HDD with MBR.. though I don't recommend it.

[oldfred]

The Windows 7 DVD is BIOS install only, but you can copy it to a flash drive and do a few updates to make it a UEFI installer.
Only 64 bit supported for UEFI boot
http://www.sevenforums.com/tutorials/186875-uefi-unified-extensible-firmware-interface-install-windows-7-a.html
Prepare an usb thumb drive, to boot windows 7 in UEFI mode
http://www.sevenforums.com/tutorials/186875-uefi-unified-extensible-firmware-interface-install-windows-7-a.html
http://forums.lenovo.com/t5/tkb/articleprintpage/tkb-id/Beta_OS@tkb/article-id/177
http://technet.microsoft.com/en-us/library/hh304353%28v=ws.10%29.aspx

If you have dual graphics, you may need other boot options. But do not know if any specific to AMD dual video:

Possible boot options suggested by ubfan1
http://ubuntuforums.org/showthread.php?t=2184839&p=12871710#post12871710

This Lenovo needed UEFI/BIOS update and it was a new system.

Installing GNU/Linux on a 2014 Lenovo Thinkpad X1 Carbon UEFI/BIOS suspend to RAM issue
http://mako.cc/copyrighteous/installing-gnulinux-on-an-2014-lenovo-thinkpad-x1-carbon

Issues are often common across models by same vendor so some may apply?

Lenovo Community Bios Access
http://forums.lenovo.com/t5/IdeaPad-Y-U-V-Z-and-P-series/z580-can-t-access-bios-setup-or-boot-menu-after-changing-to/td-p/812737/page/2

Needed this: acpi_backlight=vendor
http://ubuntuforums.org/showthread.php?t=2188199
http://ubuntuforums.org/showthread.php?t=1911972&