Here’s a brief look at the major announcements made at the Mobile World Congress in Barcelona, on Day Four:

Microsoft: Microsoft announced the availability of the Windows 8 Consumer Preview for download. This new iteration of Windows operating system introduces a new Metro-based start screen, Windows Store and Cloud integration. Microsoft claimed that Windows 8 has been designed to work on a wide range of devices including touch-enabled tablets, laptops, desktops and all-in-ones. In addition, Microsoft also announced the availability of fifth platform preview of IE 10 (Internet Explorer 10) and gave a preview of Windows’s new hardware capabilities including support for ARM based devices. The company has also partnered with Qualcomm and Nvidia to launch a ‘Windows on ARM’ developer seeding program, under which select developers will be offered a test machines running on Snapdragon S4 processors and Tegra3 quad-core mobile processors respectively. These machines will also be loaded with a pre-release version of Windows 8 in order to test and optimize apps for the forthcoming Windows on ARM PCs and tablets.

Nokia: Nokia CEO, Stephen Elop said that Nokia is focusing its efforts on locally focused apps, location services and enabling developers to take advantage from monetising the ecosystem, to retain and grow its market share in the mobile space. He claimed that Nokia is currently providing billing systems to 150 operators in 40 countries and app developers using operator billing have seen a 5x increase in app downloads as compared to credit cards. More at MobileBusinessBriefing.

Foursquare: During a keynote speech yesterday, Foursquare CEO Dennis Crowley said that he intends to take Foursquare from being just a check-in and badges service to a recommendation engine by recycling check-in data that comes through their apps. He said that Foursquare has seen 15 million downloads till now, and has signed up 750,000 merchants as of now. The company also announced yesterday that it was dumping Google Maps in favor of OpenStreetMap on its web version, although the iOS and Android apps will continue to use Google Maps.