...The PS2/USB attachment runs using standard protocols for which no driver is needed. Since no driver is needed, Happ has no reason to create any.
Just to clarify this marketing "no driver needed" PR crap...
What the full statement should say is "No extra driver needed to be installed; no need for a install disk; can use drivers already installed with windows." Everything that states "no driver needed" means the above statement, be it mouse, thumbdrive or whatever, NOT that no driver is used, nor that it doesn't work better with an extra driver. But another part that most "no driver needed" products also imply is "since we didn't need to, we didn't write a driver, so we can't help with any driver problems since MS wrote it."
Have to say on the plus side, there aren't the 1000+ third party drivers that can conflict with each other or crash the OS, like win9x and before. Although it sounds like samsung did something to the standard MS mouse driver setup in the OP's case.
Back to the OP's problem, can't help you much besides what's already said. I don't have the USB version, so I can't help with which driver is best. But good luck.