I don't think you can stop them showing (but I'm no expert), however it's not likely to make any real difference. These screens only show the progress of the boot process, so even if you stopped them being created you're not going to make it boot any faster. About the only way you could make it go faster is by disabling all hardware/devices you're not using so that it doesn't try to scan them, such as the PATA or floppy controller (assuming you don't have these types of drive fitted). That might save a second or two, but I wouldn't count on it.