I use memtest86+, and have not used HCI memtest. memtest86+ has bootable CD and USB files on its website you can download and burn to the appropriate media.
You boot to memtest86+ and it will run 9-10 different iterations to fully test your RAM. It will stop if it encounters errors, showing the errors in red font on the screen. You should use it to test each stick of RAM individually, and if both pass, then as a set.