The worst of all was Vista,
Even though I can get it to work OK, now, after the SP downloads, -—
It was arrogant as heck for Microsoft to NOT allow Vista to run Outlook Express. I did not know that when I bought my new computer, and it has been a royal pain accessing old files.
No, the worst of all was Windows ME, Windows 95, Windows 3.0 and DOS 4.0
My biggest problem with Vista has been on the GF's puter. Old system (W2K) dies, but HD's were good, she got a new system (Vista Home Premium) and tech support (me) was supposed to port everything over. Windows has a "Windows Easy Transfer" (WET) that is geared towards transferring from a working system to a new one. But they only thought so far as to "assume" that the old system was fully intact, not just a hard drive on the same machine. So manual transfer, with different filesystem sructures was a PITA.
Oh well, I've had worse; NULL modem cable between machines and Kermit transfers.