I have run Crysis in both modes without problems. It depends on how you start it, or which icon that goes to the x64 mode.
What is saying "access denied"? If you are referring to the CBS log, copy it to the desktop then open it with notepad, or wordpad, or Word.
Repair install is while running Win 7 you insert the install DVD. It should autostart and start the install. Pick your language, select install, then upgrade. You may have to reactivate after doing this. Once again, if you want to wait, use your discretion.
Maybe the CBS log will tell us how much corruption you are showing in your system.