Windows Installer - Urgent help needed

[Sam]

Im trying to install Microsoft Office, but when I press
install it says:

'The windows Installer Service could not be accesed. This
can occur if you are running in safe mode, or if Windows
installer is not correctly installed. Contact your support
for personal assistance.'

Well im not running in safe mode so that can't be the
problem, and I've tried downloading the latest version
from the Microsoft Website but there doesn't seem to be a
version for Windows XP. I've also restarted my computer
several times. Can anyone think of any other ways to solve
this problem.

Please Help I need Microsoft Office, for my Course-Work.

Thanks for any help you can give.