LTspice won't start

I have a Dell PC with Windows 10.

LTspice simply won't run - when I double click the icon, nothing happens!

I've tried right-clicking and selecting "run as administrator", and again, nothing happens.

I've tried re-installing LTspice, and that hasn't helped.

I've tried both the x86 and x64 versions, and the same behaviour with both.

LTspice is the only program on my PC that I'm having any problems with.

Any ideas? It's driving me round the bend.