I've noticed some pretty similar posts to this but nothing quite answers the main questions I have. Am currently running XP 32bit quite happily but would like to increase memory and also upgrade to some of the new generations of ATI or Nvidia GPUs (which depends on money!) at some point in the future. Running XP or Vista 32bit is obviously then a no go as they won't recognise most of the memory so 64bit will be the only option. Have heard comments in the past that 64bit OS's have more software compatibility issues so was really wondering what peoples experiences have been with 64bit and what programs people are talking about when they've said this. Am totally ignorant on this topic I'm afraid!