anybody know why wordpress on xampp cause very long time to first byte.. around 10-15 sec, im running on 100mbit box, latest xampp and latest wordpress..

When we even will help you with this particular, I believe more details are needed - if you're running it in your area, network connection speed should not matter. Maybe the specs of the machine, things like that.

On the a little more useful note (:-):

  • Try managing a network sniffer for example Wireshark (or using Task Manager) to check on what visitors are really studying the network - could it be full?
  • It is possible to process trying out plenty of CPU time, or thrashing the disk a great deal?
  • Look into the speed from the MySQL database
  • Try redownloading Wordpress and XAMPP, just to be certain
  • Re-install Wordpress (ie, run setup.php again)
  • Run the initialisation batch script for XAMPP

They are only wild suggestions, so I am unsure how helpful they'll be.