Downloaded Office 2010 Home and Student Trial not running

Hi all.
I have downloaded Office 2010 Home and Student Trial but am unable to use. When I make an attempt to open any office application I receive this error code “This program can't start because oart.dll is missing from your computer. Try reinstalling the program to fix the problem”. I have tried all MS web solutions including reinstalling but only to be failed. Currently because of this problem I am using Open Office. However, I want to use MS Office because it is much better than open office. If this is a common issue for MS Office then I better not buy it.
I am searching for help. Can anyone?
Thanks.
