Hi Peter, your catalog will remain safe. It’s normally stored in the Pictures folder by default. If you also backup each time you quit LR, you should have a backup copy in another location.
Thanks for your reply. However, despite reinstallation (x3), Lightroom still will not run. Really frustrating. I just do not know what else to do.
I am wondering if it's time for a PC rebuild (I've had it 4 x years), or even the much awaited move to an iMac.
I use both W7 and Mac and I’m sure you won’t be disappointed with a new iMac. Even the standard (non-retina) display is stunning. W10 seems to be designed for dummies.