issues deleteing peerblock 1z1p5q

I'm trying to get rid of peerblock, but file explorer won't let me delete a driver file (in the peerblock app folder on my usb drive) called pbfilter.sys, because it's apparently still "open in another program". Honestly I don't know a lot about how .sys files work other than that they're for the computer to read & not me, but it looks like it's not running, it acts like it's not running, and it doesn't show up in taskmanager, so I'm stumped. apologies if this is an issue that's been asked/resolved before, or if this is the wrong place to ask.