If you added W8 to a pre-existing W7 PC, then you'll probably find that the boot files are still where they were on the single W7 system.
If that's on a HDD which you wish to remove/format, then you'll need to get W8 booting from a location which is staying. Changing the Boot Partition
If W8 is already booting from the right place, or after doing the above, you can simply delete the W7 entry from the BCD (yes EasyBCD does that) and do whatever you want with the W7 partition.
(Why would you want to get rid of W7 and keep W8 ? )
I had Win 8 installed but can't update to Win 8.1 because Win 8 updates fail.
I installed Win 7 hoping I could update it to Win 10 and ended up with a dual boot.
When I started computer both showed up and I had to select one of them. Both Win 7 and Win 8 will boot up..
I removed the Win 7 boot. But the Win 7 is installed in same partition as Win 8 in the "C partition".
How do I find Win 7 installed files so I can delete them?