Small but annoying problem

After I press the power button on my Dell Dimension 8200 computer, the splash screen ( for those who don't know, it's the screen that shows that big blue Dell logo at startup ) comes up as randomly placed vertical blue bars or sometimes it just doenst' show any splash screen and goes right to the Windows XP startup or sometimes, the normal splash screen is there but it's extra small and has just about 2 other exact copies of it underneath it. This just started lately and I haven't made any changes to it. My virus scan says my computer's fine, but I just get the feeling there's more to it. It doesnt' interfere wtih any other features on my computer, just the splash screen. Like my subject title says, its' a small but annoying problem .