WinPro7 machine started acting odd during bootup. The initial screen you see when it is booting that says "Please wait" seems to stall indefinitely. We have to hit the button on front of box to reboot. Once we reboot, the black window that gives options to boot normally or in safe mode comes up and then it boots fine. What do I need to check to figure out what is hanging it up? We do have Avast on this machine and I suspect it has something to do with the boot hang.