If you’re like me you probably use Microsoft Calculator (calc.exe) a fair bit. I still end up dragging out the TI-89 or Googling to do conversions though. It seems as though this is a problem for someone at Microsoft too, because today I found Microsoft Calculator Plus which is the standard Windows calculator, PLUS a new skin (you CAN switch it off under View->Classic View) AND the ability to do common conversions. Enjoy!