>I have application as Top-Level Form(without Screen).
>Can I remove application's icon from taskbar?

As Mike said, you can use the Windows API to do this. Try the following:

declare integer FindWindow in user32 string,string
declare integer GetWindowLong in user32 integer, integer
declare integer SetWindowLong in user32 integer, integer, integer

#define GWL_EXSTYLE       -20
#define WS_EX_TOOLWINDOW  0x80
#define WS_EX_APPWINDOW   0x40000

do form mytoplevelform name otemp noshow
local nhwnd,nstyle
nhwnd = FindWindow(0,'Top Level Form Caption')
nstyle = GetWindowLong(nhwnd,-20)
if bitand(nstyle,WS_EX_APPWINDOW) = WS_EX_APPWINDOW then
   SetWindowLong(nhwnd,-20,bitxor(nstyle,WS_EX_APPWINDOW))  && remove taskbar force style from Window
   nstyle = bitxor(nstyle,WS_EX_APPWINDOW)
endif
SetWindowLong(nhwnd,-20,bitor(nstyle,WS_EX_TOOLWINDOW))
otemp.Visible = .T.

The only drawback that I see with this technique (and there could be others) is that because you are changing the style of the window, the icon doesn't display in the upper left hand corner of the form.

HTH.