system tray problems with Win98

Hey

this code belows works fine on XP and "some" Win98 machines.
what could be the issue here?
the app still runs after executing this code but no trayicon is added. neither an empty spot or the icon.

Dim ICONDATA As NOTIFYICONDATA
ICONDATA.cbSize = Len(NOTIFYICONDATA)
ICONDATA.hWnd = SYSTRAY_HWND
lngIconHandle = FreeIconHandle()
If lngIconHandle = 0 Then Exit Function
ICONDATA.uID = lngIconHandle
ICONDATA.hIcon = ExtractIcon(SYSTRAY_HINSTANCE, SYSTRAY_ICONPATH, SYSTRAY_ICONINDEX)

ICONDATA.szTip = SYSTRAY_TOOLTIP & Chr(0)
ICONDATA.uFlags = NIF_TIP Or NIF_ICON Or NIF_MESSAGE
ICONDATA.uCallbackMessage = PK_TRAYICON

If Shell_NotifyIcon(NIM_ADD, ICONDATA) Then
AddIcon = ICONDATA.uID
End If

DestroyIcon ICONDATA.hIcon

Ive solved whe issue by myself.
actually I cant figure out what was actually the diffrent between

taking the size of the structure (didnt work) or my own variable declared as the structure.

but it it made it work.