XP SP2 Makes a Hash Of It
Yet, on my second XP SP2 installation, it totally destroyed and hosed my computer. It took a superhuman effort (with Google and MSDN help) to recover it.
Briefly, here's what happened:
The computer being upgraded (a 4 year old Dell running XP with .5 Gig of Memory and 40 G of Disk) lost connectivity to the server that had the upgrade pack on it (due to a wire being unplugged - duh.) This aborted the upgrade, and which caused the upgrade to try to unwind itself.
Up to a point when one of those famous "about to install unsigned software, do you want to proceed " messages that I love so much came up, quite unexpectedly. Being suspicious of what might be going on, I said "no." Everything seemed fine.
Later on, when I tried to reboot, it failed, hard.
Over and over again, blue screen of death! Booting from floppies didn't work. Booting from CDs didn't work. Booting to DOS worked, but when I tried to look at the C: drive it said that it wasn't there.
Anyway, long story short , after a bit of searching I found that I was not the only one. And Microsoft, God Bless em, had a technote that took me through a tortured process of cutting 8 floppies, booting of of them into the "Recovery Console", lighting some incese, and following a bunch of steps. And yes, I am back up again,without SP2 installed.
So I guess this is the exception that proves the rule.