Private Declare Function GetTickCount Lib "kernel32" () As Long

Private Sub Timer1_Timer()
    c = GetTickCount
    h = c \ 3600000
    m = (c - h * 3600000) \ 60000
    s = (c - h * 3600000 - m * 60000) \ 1000
    If (m < 10) Then mm = "0" & m Else mm = m
    If (s < 10) Then ss = "0" & s Else ss = s
    Label1.Caption = "Время включения: " & h & ":" & mm & ":" & ss
End Sub

Label1.Caption = "Время включения: " & h & ":" & mm & ":" & ss