I've never done an express install so I'm not sure, but it may not be able to find or create a partition to install Windows on to. You may have to delete and recreate a partition by going custom; it's pretty much self explanatory. If you have more than one drive installed one will be labeled 0 and the others 1, 2, ext. If you don't have anything at all you want saved on the drive you're installing to, you can delete all the partitions on a particular drive (watch the number label) and create a new partition for the OS (this may create several partitions). Everything else should be the same for express instillation.