Windows XP Startup

I have a Dell Vostro 200 slim tower with Windows XP Pro installed. It seems that every time a restart is performed, I see the Dell splash screen and then the Windows XP splash screen; after this it goes to a ‘black’ screen and nothing happens. It is able to go as far as me logging into the PC, rarely. I have done all of the Windows updates, and thought that fixed the issue, but still nothing. This is driving me nuts!! What is happening here???

Please H E L P ! !