Hi, you all
I have 2 Windows 8 PC's in a network connected with some D-Link gigabit router and all PC's have gigabit ethernet cards. They all have IP addresses entered and subnet masks.

at the very beginning, its speed was great, but now one of it have a slower speed.I did not touch anything and do not know what's wrong with it. i did not find a good solution for long time google.

what do i do ? please help me? many thanks in advance.

You have to remember that unless you have a RAID array or Raptors your hard disks aren't gonna be transferring data at more than about 50MB/s (Thats for a high end 7200RPM 8MB Cache model too) so basically your pretty much limited by your HDD.