partition created to install Ubuntu appears as "unusable"

I followed all the steps I read and/or watched about installing Ubuntu 16.4.1 LTS alongside window 7,

I made a partition in Drive C with enough space for Ubuntu, but when it begins installing, the free space which I intended to reserve for Ubuntu appears as "unusable" instead of free space. Also, the (+, - ) buttons are inactive and give me no way to add a swap area or whatever. What should I do to complete the installation? I'm new to Ubuntu.

Solution 1:

The differences between MBR and GPT are e.g. explained in http://www.howtogeek.com/193669/whats-the-difference-between-gpt-and-mbr-when-partitioning-a-drive/. As your disk is probably partitioned with MBR partition table, it is not easy to convert to GPT without data loss (see e.g. http://www.thewindowsclub.com/convert-mbr-to-gpt-disk or http://www.disk-partition.com/gpt-mbr/convert-mbr-to-gpt-without-data-loss.html, all using special software and being meant for mor 'insiders').

Before proceeding, be sure to have an actual backup of all your important files!!

As MBR allows for more than four partitions, when one of the four is a so called 'extended partition' which contains 'logical partitions', the easiest way for you to proceed would be:

• Make a backup of the contents of the last partition (there are only 113 MB used, so should be no problem to copy the content)
• Delete the backuped partition; this should give you continuous space at the end of the disk; so there are only three partitions left
• If you need to have the fourth ntfs partition again, create it as 'logical partition', so the fourth partition should be automatically created as 'extended' and the new one and all others created from now on will be 'logical'
• Now the space left should be available to linux for partitioning

If you do not need the fourth ntfs partition, you could skip the step of creating it, and install linux in the available space; the installer should create logical partitions as needed (for '/' and 'swap').

The above description implies that the partitions are in 'disk order', which means their starting blocks are in ascending order. To make sure, you can maybe use the windows disk manager, or start your PC from a linux live disk and run gparted to get reliable information (and do the partitioning).

Edit:

I did not talk about your backup, but about the fourth partition on your disk (sorry for being not precise). Do you know what is on that partition (should be something like drive D: or E: in windows)? If there is nothing important, you just can delete the partition (in windows disk manager or with linux gparted). If there are important files, copy them to a secure place before proceeding.

As I am not a Windows user, I do not know how to create extended/logical partitions from Windows (I was not able to do so in windows disk manager, only from the commandline diskpart (with administrative rights) and there after select disk 0 doing create partition extended.).

If you do not need the fourth partition (drive D: or E: or whatever), just delete it. When installing Ubuntu, you will be able to use the free space now and the installer will create an extended partition automatically.