Maximized window still shows resize corner

Compared OS:

• ReactOS bootcd-0.4.11-dev-532-gd5cced1-x86-gcc-lin-dbg
• Windows XP Pro x32 SP2
• Windows 7 Pro x64 SP1

Tested software:

• Bulk Rename Utility x32 3.0.0.1
• Windows XP regedit.exe
• Foobar2000
• ReactOS explorer.exe
• Windows XP explorer.exe
• Windows 7 explorer.exe

Example taken from XP regedit.exe, the same behavior in other software.