you too can use your install USB stick kernel to boot slack, then take care of it. I got get the particulars on that, because it is using the usb stick kernel. But I think it is as easy as booting it using the usb stick and it has the instructions right there in front of you, all you have to know where where your boot partition is? then install grub update it reboot?

it has been a long time sense I had to do something like that, so its a little scratchy in my head on how it is actually done. I just do it like I posted in my other post up above this one.