Microsoft is expected to unveil new versions of the Windows computer operating system today that will accelerate a generational shift in computing with potentially wide-ranging implications for many users.

The updated versions of the software have been written to run on 64-bit machines - PCs and servers that can process and store information in single "blocks" that are 64 characters long, double the length of the blocks on current machines running Windows.

The extra capacity speeds up data-intensive tasks, such as processing sophisticated computer graphics or searching large databases.