In order to install Windows 7 you need at least 20GB of hard disk space and 2GB of RAM. However with those minimum requirements windows 7 will run very slow and in a short time you will see that you can not make updates to the operating system or security for lack of disk space.
So I recommend that you have on hard disk about 50 GB free (which will allow you to migrate in the future to a newer version of windows such as version 10) and in terms of RAM if your computer has installed 4 GB of memory you will see how you can use your computer with good speed and performance.
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In order to install Windows 7 you need at least 20GB of hard disk space and 2GB of RAM. However with those minimum requirements windows 7 will run very slow and in a short time you will see that you can not make updates to the operating system or security for lack of disk space.
So I recommend that you have on hard disk about 50 GB free (which will allow you to migrate in the future to a newer version of windows such as version 10) and in terms of RAM if your computer has installed 4 GB of memory you will see how you can use your computer with good speed and performance.