When booting up computer just goes to a black screen. Nothing happens before this it just goes straight to a black screen with nothing on it. The screen and mouse don't turn on, neither does the keyboard.
The first thing to do is make sure you don’t have any removable media inserted into the computer whether it be a CD, DVD or USB storage device. Next, you will want to see if you are able to boot into safe mode by pressing F8 while Windows is starting.
Also, the Windows XP End of Support date is now less than a year away. It is strongly recommended to make the move to a modern operating system such as Windows 7 or Windows 8.
A recent Springboard blog post written by Stephen Rose covers what end of support means and has many helpful links to the free tools you will need to migrate from XP to a modern operating system, whether it be Windows 7 or Windows 8.
Another resource to consider is the Springboard Series on TechNet which contains articles and videos to assist with your operating system migration as well as manage your new environment once it is in place.
Do you have another monitor you can attach to the computer to test to make sure it is not the monitor? Of course that wouldn't explain the mouse or keyboard. Have you checked the monitor connection and power? The only reason I suggest it could be a monitor issue is that I recently had a problem with the monitor "blacking out". Replacing the monitor solved the problem. But that may not be the case for you. How have you determined the mouse and keyboard do not turn on?