did you delete them from the camera when you copied them over?
if you did not then the easiest way is probably to delete all the relevent pictures off your computer and then copy them over from the camera again (double check that they are on the camera before deleting them from the computer though)
If they are not still on the camera then, when you can see the list of pictures you want to delete click on the first one you want deleted, hold down shift and click on the last one you want to delete, this should highlight the two you clicked on and everyone in between. now just press delete.
just to raise another point, I seriously doubt that you will be able to email 40odd pictures to anyone in one go, unless they are very small low resolution pictures then 40 of them is certainly going to be to large for a single email. you might have to attach them 10 at a time and send 4 mails.
To attach multiple pictures to one mail use the same method as I described above, when browsing for the pictures you want to attach simply click the first one you want to attach, hold down shift and then click the last one you want to attach and all between will be selected too, now just press OK and all selected pics will be attached.