Loop, 100% CPU Usage, using sleep doesn't work?

Question

I have this small application written in MASM that keeps checking for an Active internet connection and sends a Beep if there is one, now my problem is that the loop uses 99% of the CPU, I have tried putting a Sleep inside the loop but somehow that isn't working ?

This is the code:

;build as a WINDOWS app

        .XCREF
        .NOLIST
        INCLUDE    \masm32\include\masm32rt.inc
        INCLUDE    \masm32\include\wininet.inc
        INCLUDELIB \masm32\lib\wininet.lib
        .LIST

;-------------------------------------------------------------------------

IsOnline PROTO   :LPSTR
Sleep PROTO STDCALL :DWORD

;-------------------------------------------------------------------------

IFNDEF FLAG_ICC_FORCE_CONNECTION
FLAG_ICC_FORCE_CONNECTION EQU 1
ENDIF

;-------------------------------------------------------------------------

        .CODE

IsOnline PROC    lpszURL:LPSTR

;Test Internet Connection
;
;lpszURL points to a zero-terminated test URL string (must start with "http://")
;
;Returns EAX = FALSE if not connected
;            = TRUE if connected
;        EDX = connection description (see InternetGetConnectedState documentation)

        push    eax
        mov     edx,esp
        INVOKE  InternetGetConnectedState,edx,0
        or      eax,eax
        jz      IsOnl0

        INVOKE  InternetCheckConnection,lpszURL,FLAG_ICC_FORCE_CONNECTION,0

IsOnl0: pop     edx
        ret

IsOnline ENDP

;-------------------------------------------------------------------------

szURL   db 'http://www.google.com',0

;-------------------------------------------------------------------------

_main   PROC

loop00: INVOKE  IsOnline,offset szURL
        Invoke Sleep,5000
        or      eax,eax
        jz      loop00

        INVOKE  Beep,750,1000
        exit

_main   ENDP

;-------------------------------------------------------------------------

        END     _main

Answer 1

Sleep() may trash registers and so the return value from IsOnline() may be lost.