Free Microsoft software can be obtained through Microsoft Imagine (formerly Microsoft DreamSpark).
The software and related keys can be obtained from Royal Holloway portal. If you are given a choice, please opt for Imagine/DreamSpark Premium.
This programme entitles the users to one key of most pieces of Microsoft Software, including the latest operating systems (Desktop and Server), development languages and server software.
The notable exception to the extensive catalogue of software is Microsoft Office, which is not considered ‘development software’ by Microsoft. This can instead be obtained for home machines by logging into the Royal Holloway Office 365 portal, clicking the ‘Office 365’ button/banner on the top right, and then choosing ‘Install Office’ on the top right.
More information on Microsoft Imagine programme can be found on the Microsoft Image page, and on the Wikipedia Page.