I noticed that, by default, my PC synced to internet time only once a week, far too long on an old PC. I have downloaded a package (atomic.exe) that allows you to program any chosen interval and hope now the PC clock will be very regularly updated to internet time. This is essential for WSPR. At the moment it is set to sync every 5 minutes, but once every few hours is probably frequent enough.
I used atomic.exe before on my previous PC for many years. It worked well. A virus scan showed no threats. For now I'll stick with this, although (see comments below) there may be better solutions when the internet may be down, but this is very rare. Virgin Media cable seems very reliable and very fast.