So I have not done one thing with Cubase!   Should I delete it?  Would CWB run better without it?
THANKS,
AB

Shouldn't make any difference to CbB whatsoever
 
You will gain some extra disc space, depending on how much else was bundled with Cubase
The core program itself won't need huge amounts but the full installation could be around 8/9Gb

Yes, don't be a trader!!!
...but seriously I have Sonar X1, X2, X3, Platinum, Harrison Mixbus, and Tracktion Waveform on mine.
Oh, and Cakewalk.

Can't hurt to keave it installed...

I imagine you can use all it's vst/vsti devices in CbB...

If you can reinstall it easily, sure delete it. Why have something you don't use? On the other hand, I still have Cubase AI on mine, but that is a much smaller program. I only leave it on because it's a pain to reinstall, I have to find the code that came with my UR-22 interface, as it was an add-on. But I wouldn't leave the full program on if I didn't use it. I do also have Reaper, but that is a very small footprint.