Hi! Well, I think it's definitely a drivers issue; a video card drivers issue. You said that when you boot into Safe Mode you don't have any problems, right? IF so, then you have a drivers or application problem in this case related to your Video Card. LEt me ask you this: That ATI icon on your systray, it corresponds to what? What is it exactly that it's loading? An ATI application?
When I said if you hear any beeps, I meant immediately after you turn on your PC, after two seconds. If so, you need to pay attention to the pattern like I said before and post it here,ok? If you don't have any beeps, have you tested your RAM sticks? You can run memtest86, it takes long hours but it is the most precise tools to determine if RAM is bad, which cause lock ups or crashes. You can download it for free at www.memtest86.com,
create a floppy disk or a bootable CD, insert it in the CD drive and start the PC...let it run overnight and even longer. I'd try to uninstall the video card and all its applications and drivers and resintall everything from zero...Did the Video Card come with a CD with drivers? If so, just install drivers, no applications for now and try to boot normally. Post back with results and more info,ok? Good Luck!