Nostalgia machine, hooray! Loved the tones of speech in the readme and the swf files, just perfect for that time/vibe. The sites too, all the references, awesome.
I feel like more of all of it would be nice to add even more immersion, even though what there is is already awesome on many fronts, don't get me wrong, but more content was needed to tip over the edge to me, let's say.
The responsiveness and design of the buttons and windows felt simple and perfect IMO, as it should to mimic Windows and the jokes were funny.
I also specially liked the mistakes and imperfections and overall roughness of the animations, I can almost see what the animator did when making those, lol.
And I guess I'd have the player be able to, say, delete, create and edit files and all that jazz if I was seeing this as 5/5, even if that wouldn't contribute to the jokes too much, but just for the immersion, again. Anything to make you believe you're in Windows XP and not in a parody of it (except when you enjoy the jokes).
But still, overall solid parody and throwback, loved it!