Not least savvy just unsuspecting through lack of knowledge I would suspect.
You have been badly served by having two of M$'s less good operating systems!
In my opinion Millenium was awful and Vista was only slightly better! It is interesting to observe how M$ can build fundamentally good operating systems like W98 and XP and equally fundamentally awful operating systems like Millenium and Vista!
I went from XP which I liked to W7. I downloaded the W7 Release Candidate made my PC at the time dual boot in case W7 was a dog but after a day or two never used XP again and pre-ordered a copy of W7 when the initial version was offered for general sale.