Install Ubuntu on disk with Windows with both GUID and MBR partitions

This is actually a reminder for me. The original answer is found at askubuntu.com.

What I had done in my case was the following:
I was in a new PC where everything required SATA connections. I thought my old ATA optical drives would work but no chance obviously. My only solution was to use the one and only 4GB USB stick I found somewhere roaming around the house.

At first, I installed Ubuntu 12.04.  I created my partitions etc. I then had to delete my 4GB in order to get Windows into it. Unfortunately, I found no way to install Windows 7 without deleting Ubuntu 12.04. So... I formatted the whole drive once again and I installed Windows. Now I was ready to install Ubuntu. In this case, I decided to install 13.10... But!

Ubuntu 12.04 had created a GPT record. Windows deleted the partitions found in this GPT record but not the record itself. Instead, it created its MBR record - leaving the GPT record intact. Empty but still there. As a result Ubuntu read the whole disk as unallocated space since it preferred GPT over MBR.

I got into Windows safe mode and did the following:
bootrec /fixmbr
bootrec /fixboot
bootrec /RebuildBcd

No luck!

I googled once more and found the answer linked at the beginning. From Ubuntu 13.10 live, I did the following:
a) Installed gDisk

sudo apt-get install gdisk

b)Then listed the partitions that are on the GUID partition table:

sudo gdisk -l /dev/sda

c) They had come up empty. I had to preserve the MBR and drop the stray GUID partition table identifier entirely:

sudo fixparts /dev/sda
w

That was all!