Both computers got a Vista experience rating of 1. Neither would play a DVD decently. Vista is due for lots of updates and service packs. That will bog it down even more --->>
2.5ghz-1024mb-64mb video card
2.8ghz-1024mb-256mb video card
looks like your 2.5 ghz pc doesnt have a directx 9 card, if you dont have one of them you will have troubles.
Service Packs and updates dont necessarily bog down a PC, with the superfetch Vista enables a more dynamic page file system that, unlike XP, deals more efficiently with files.
I need to find you this article I read earlier today. The author reviewed Vista on several different machines, from a 5 year old p3 upto a modern core duo. The most money he had to spend was 50 dollars to replace an old video card to get Vista to run properly.
One other question, what gave you a rating of 1?