Huge Computer problem..

[VeZ]

I turned on my computer the other day to get this message:

"Windows Product Activation
Some system files are missing or damaged. You cannot log on at this time. Please use your installation CD to reinstall or repair Windows. Error Code:0x80040507."

Ive heard I should be able to boot up from the disc or press f8 to go into safe mode and such, but the problem is, whenever I used to start my computer up, the first thing I would see is my desktop. I never see my cpu specifications or black and white text or the windows xp loading bar, it just goes straight to the desktop.

So in a quick summary, I've tried getting to the BIOS screen, pressing the delete key at startup, etc. But I can never stop the computer before it tries to auto log me in to the computer. Am I completely screwed here? Oh and it does bring me to my desktop, but I only see my wallpaper, nothing else. No start menu, icons, nothing

 

[Dizzymon]

Just hold the F8 key if you don't see anything and see if you can boot into safe mode.

 

[VeZ]

Ive tried it and either my computer monitor stays black, or it goes to the welcome screen.

Its almost as if I do get F8 to work, but I just cant see it on the screen. Because at one point I pressed f8 a bunch and sat there for 30 seconds and my computer monitor stayed black.. but then I pressed enter to see what would happen and then the welcome screen showed up...cause when you press f8 doesnt it give you a list of options whether to start windows in regular mode or safe mode? its really hard to explain :\

 

[The Bakery]

Can you boot using the windows XP CD?

Edit - Did this happen out of the blue? New hardware? Software? Virus? Abnormal shutdown? Power outage, etc?