You're welcome.
Sorry, the NO relates to should I be worried, which in my haste I didn't post.
There is no (or should be) need to get rid of it, it is doing no harm in its inert state, should you have installed that program, then Avast would scan its contents as it is unpacked to install the program. Any potentially harmful element would have been detected at the point of unpacking and prevented from running.
If however you no longer need this memtest86-usb.zip file in your downloads folder then yes you could remove it.