Too help the readers, I think you'll need to tell people what specifications your computer has.
*Operating system (Windows XP, Vista, 7 - 32bit or 64bit)
*Hardware - Graphics card, CPU, RAM etc.
*Software - Did you download the game or buy it in-store?
*Have you defragmented your PC lately? Are your registry files corrupted?
*Who installed the Graphics card? Has it been installed properly?
Need more info as it could be anything.
More information and I reckon people may be able to help.