I originally started playing with RHEM but never did end up finishing it, not due to being stuck but other games at the time had my attention being drawn away (friends nagging to play online games at the time). I then picked up RHEM 2 and then 3 and finally went back to the beginning after playing RHEM 2 for a short while. I don't like skipping ahead any games usually and since I was really enjoying RHEM 2, I went back to the very beginning. I have to say this series is fantastic, expecially if your a fan of hard puzzles, many switches when you flick them, they do nothing at first.
RHEM series is a project from one developer, his name is Knut Müller and don't let a one man team have you thinking this game will be mediocre. Its far from it, its along the lines of being brilliant to make a game, let alone a series of games by yourself, and sell them very well because they are greatly enjoyed. As the previous reviewer has suggested, you WILL need some sort of way to graph a map of the game, as well as hints/notes to the puzzles. This is a serious mind bender with puzzles and if you are like me, I won't use cheat guides in adventure games. You will be stuck unless you take notes and draw a map or resort to cheating (if you do go this route, do use UHS Reader as it doesn't tell you the exact solution right away, but little hints instead). Of course this takes me so much longer to finish a game, sometimes not finishing it at all yet, but its much more enjoyed that way. Thats at least how I feel. The accomplishment of a puzzle with the magnitude of this game is so rewarding when you see the ending.
For the game to run, expecially for XP/Vista/Win7, RHEM 4 will run flawlessly but as I have suggested to try RHEM, make sure you have Quicktime installed. Any adventure game fan should have these in their collection.