How can I install Ubuntu instead of Windows 7, but format the partitions and choose their sizes?

Solution 1:

Partitions merely for organization isn't a great idea. Folders can handle this job just fine.

Partitions are fairly rigid because they can be difficult to resize. We can see from your Windows setup that you ran out of room on your primary partition where Windows was installed. What's to stop the same thing from happening in Ubuntu?

It's probably better to just accept the default options for partitions and use folders for organization instead.

Some people like to keep a separate /home partition for easier formatting and system reinstalls, but reusing that /home on a different system can end up being a bit more complicated in practice. Lots of software store configuration files under /home and these configs won't necessarily work out-of-the-box when a /home partition from one installation is used on a different version, flavor, or distribution. It's possible that a separate /home partition could save you some time in these scenarios, but you should plan and expect to do some tweaking to get everything working smoothly.