Used by the Backup and Restore Center Control Panel, the Block Level Backup Engine service allows for a Complete PC backup at the block level of a disk, instead of file by file (not available on the home versions). This is often referred to as an image of the disk (or partition). If you don’t plan on using the Backup and Restore Complete PC feature then you won’t need this service, though because it is set to manual by default, it doesn’t use any system resources, so you won’t gain anything by disabling it.