Hi ilham18,
Some questions first!
[1] Are the files you are deleting on your HDD [C:\]?
[2] Have you got any other HDD's or removable media [Flash drive, USB etc] attached?
[3] In the Registry Settings, look under:
User Key: [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
Value Name: NoRecycleFiles
Data Type: REG_DWORD (DWORD Value)
Value Data: (1 = enabled restriction, 0 = disabled restriction)
Does it show 1 or 0?
[4] Do you have Norton installed [I think it has Recycle Bin Protection which could be enabled]?
I hope this helps!