My screen saver VB program cannot stretch on Screen.

Hi,I put my codes about screen saver program with VB into the following,please you checkout it.Thank you. If these things are not clear please tell me. Thanks a lot.

Option Explicit
Dim prevX
Dim prevY

Private Sub Form_Click()
exitScreensaver
End Sub

Private Sub Form_DblClick()
exitScreensaver
End Sub

Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
exitScreensaver
End Sub

Private Sub Form_KeyPress(KeyAscii As Integer)
exitScreensaver
End Sub

Private Sub Form_Load()
frmMain.Width = Screen.Width
frmMain.Height = Screen.Height
frmMain.Top = 0
frmMain.Left = 0
Select Case GetSetting("Saver", "Settings", "DrawSpeed", "5")
Case 1
tmrMain.Interval = 1000
Case 2
tmrMain.Interval = 900
Case 3
tmrMain.Interval = 800
Case 4
tmrMain.Interval = 700
Case 5
tmrMain.Interval = 600
Case 6
tmrMain.Interval = 500
Case 7
tmrMain.Interval = 400
Case 8
tmrMain.Interval = 300
Case 9
tmrMain.Interval = 200
Case 10
tmrMain.Interval = 100
End Select
End Sub

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, _
x As Single, y As Single)
exitScreensaver
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, _
x As Single, y As Single)

If ((prevX = 0) And (prevY = 0)) Or ((Abs(prevX - x) < 100) And (Abs(prevY - y) < 100)) Then
prevX = x
prevY = y
Exit Sub
End If
exitScreensaver
End Sub

Private Sub Form_Terminate()
exitScreensaver
End Sub

Private Sub Form_Unload(Cancel As Integer)
exitScreensaver
End Sub

Private Sub tmrMain_Timer()
Dim x, y, r, g, b, radius
x = Rnd * frmMain.Width
y = Rnd * frmMain.Height
r = Rnd * 255
g = Rnd * 255
b = Rnd * 255
radius = Rnd * 800
frmMain.Circle (x, y), radius, RGB(r, g, b)
End Sub

Just now I put it into Control Pannel on Win2000 and it's OK.But it cannot be run under winXP.
When it runs it appears in title bar of form on screen. When I double click the bar the size of form change into max size as like a normal screen saver so everything about it be ok.