Look for this in psclient.cfg try adjusting it, tho it just sizes the border and does not resize the screen...
; Width/height of CrystalSpace visual
Video.ScreenWidth = 1024
Video.ScreenHeight = 768
or try
; Screen depth (currently supports 8, 15, 16, and 32 bits, NO 24 bits!)
Video.ScreenDepth = 16
; Use full-screen mode if available
Video.FullScreen = no
Change video fu.llscreen to opposite than what you currently have and resize in windows