I shut down my pc yesterday and turned it back on today, I presssed the power button on the tower and the pc makes the hard drive sound and starts whirring but i see a black screen and it just keeps making booting up sounds without actually booting up.

Also i do not see anything on the monitor while this is happening not even the the "packard bell boot screen" which is before the xp progress bar bit.

Please help, thanks. By the way this question is not posted from the pc, its from my brothers laptop.

many things can cause your situation, maybe its the monitor that is not working ,hook it to you brothers laptop to test it !
http://www.computerhope.com/issues/ch000801.htm

it could be your video card ,or you power supply not working properly!the list go on and on ! open it up and remove and reseat,ram, and pci add in cards ,and harddrive and cdrom ribbon cables !

There can other problem too.Power off your pc.Try to take off the battery from the motherboard.....wait some minute....take in...and power on your pc.....
Else
Power off your pc,
there is a 'jumper' around the battery it was set to 1-2
take off the jumper and put it through 2-3...wait some minute and put it back to the standard settings 1-2.Power on
I hope I help you