How do i install windows on a hard disk ? (readmoresoyoucanunderstand)

That shows the actual size of the drive much better in WE. The other screen you posted showed limited portions only as far as the actual drive size.

You are still working from one main drive but tell me you didn't install the Developer Preview? That was last seen in Sept. 2011 being an pre-beta build. You won't be able to much in that as you would if you had installed either the Customer Preview while that was out or the Release Preview. CP being equal to beta. RP equal to Release Candidate as far as 8 is concerned.

The recommendation here before adding the E partition would have been an option if you have an external drive available to store a full system image back up of the drive there before proceeding with other then the retail release for 8. Even with two retail versions any large drive change would be better off seeing an image created in case of any mishap.

I wouldn't be able to say if the DP build will be able to automatically add 7 into it's own boot options which is what you would normally see with a later build without problems since it was an early preview you could run on VM without any changes made on the drive. The evaluation with that will automatically expire on Dec. 15, 2012 as you will notice being 1 1/4yrs. after it's release. So you wouldn't have that on long.