When loading Zwift, some of the “witty slogans” (e.g. Respect your Ride Leader, Rest Days are Important) go by pretty quick, but sometimes the loading stalls on one (or several) for a couple of minutes or more. Eventually, it gets by and the program loads and then there is no problem. But the process to get to the Ride On screen can take up to five minues.
I am using a recent Windows desktop with decent CPU, etc.
Buy a 120GB SSD, swap the power/data cables over and clean install Windows 10 onto it. £15/$20, will dramatically improve absolutely everything about the PC including Zwift load times, which will be about 30secs. Job done.