[I Can't Reinstall B-Team]

by "opening" you meant you clicked the Play button? was the modpack already installed?

the "Unable to delete" is because you had the launcher window up and running (and both the launcher and minecraft uses java). Try closing it before you start scooping through the folders

​Ah yes, I have had the modpack installed before trying to reinstall. And yes, I do mean play button.

[I Can't Reinstall B-Team]

First things first, this is my first time posting on this forum so, Hello! 

But anyways, I tried opening B Team up and nothing happened, so I tried everything from closing all programs to closing my computer down, but nothing made it work. And in doing so I decided to reinstall B team from the Technic Launcher. In which case, it didn't. And why? It says that it was enable to delete file from the location on my computer. So I manually went in to delete some stuff and said "Unable to delete since this was opening in Java SE". So please help me, I really like what these mods have to offer, so if you could, lend a helping hand.