Is it safe to install on my current XP SP2 OS?
Could it make my PC run slower??
Is this just a new Visual Style or something similar? Or is it some early version of Longhorn?
If its a visual style, its probably pretty safe, and you can always go back to regular looking XP. Its probably not going to make your comp slower, if it does it should be slight.
If its an early version of Longhorn, then go ahead and install it, but not over XP SP2, because its likely not goign to run very well, few programs will work, some hardware won't work, and it will likely not be very stable.