OK, back from my appointment.
Here is what I did wrong: I looked at Drive C total capacity of 813gb and thought "that's about 200gb short of a terabyte - 100 for my partition and 100 for my botched vhd." Then you suggested looking at Disk Management, and the whole of Drive C is laid out - at this moment it is 813.91gb primary partiition, 97.66gb for the partition I created, PLUS 18.47gb Recovery Image D: partition and a couple of other bits - 1023mb also devoted to recovery and 360mb "EFI System Partition". What I forgot is that a gigbyte is 1024 to the power of three bytes: so, (813.91+97.66+18.47)x1024^3=998,622,845,992 bytes plus a few megabytes and you have what passes for a terbyte.
I think with my new computer and not having the available hard drive capacity in my head (as I usually do) and getting all over-excited and confused by my first experience of Windows 8, I jumped to a (wrong) conclusion. I think I also looked at the HD available capacity right after I deleted the VHD and it stuck in my brain that it was still the same as before I deleted it, (I was probably wrong then, too) so I sighed, got on with other set-up jobs and went back this afternoon to researching how to recover what I thought was lost capacity.
What a saga. Sorry to have troubled you, but I learned a few more things. (My first computer was an IBM PC with two(!!) 5 1/4 disk drives.)