They can play on US XP, if you set your language settings to Japanese.
They are only in Japanese, but there are English fanlations for Shuffle! and Prism Ark in the works.
A combo containing Prism Heart, Prism Ark and the Prism Ark Fandisk was released last year (the Love² Maximum package) for 14800 yen. You may want to purchase this one instead of the games separately (Lain-sama, I should have kept my double copy! Nande~, I blame you! 
).
The Prism Heart edition in it is a renewed Windows edition, XP-compatible. I’m not sure whether it contains the characters from the Dreamcast edition, though (if it does, you will need a kouryaku, believe me: to complete Reeds, you need such an impossible to find trick that I always wondered how anyone ever found it!). For the record, I wrote a kouryaku about it last year or so.
A recommendation though: ignore SHUFFLE!, save if you can get it for cheap. It’s not worth being paid full price. :?
I second the ‘SHUFFLE! being a waste of money’ point of view, and extend it to everything by BasiL/Navel except Cherry Petals Fall Like Teardrops, and to a lesser extent Two One and Soul Link.
You wouldn’t be “Asceai” from the Gemot, would you? 
I personally think 21 -Two one- is a quite good game, with interesting characters, plot and system. I also liked the theme a lot. Early yandere = win!
Yes. If raving about Devil on the G String didn’t give it away =P
It’s alright, and I do like it a bit more than the rest of Navel’s tripe, but yeah, Cherry Petals 
I still had a doubt, yes, but it started my suspicion! The English speaking eroge world is small, heh.
Correct, and my quote is as well robo. I happen not to have a dislike for the game, especially for the concubine robo. :mrgreen:
In fact, it’s one of my favourite erogames robo.