Have you tried right-clicking on the shortcut to the program, or the .exe, and selecting the "Run As Administrator" option? Do so even if your user is an Admin.
Try right-clicking on the actual Setup.exe and selecting the "Run As Administrator" option? Do so even if your user is an Admin.
Have a look at the Access Permissions for the folder C:\Program Files (x86)\Common or maybe you mean C:\Program Files (x86)\Common FILES?
HOW TO: Take Ownership of a File or Folder in Windows XP (or Vista or Win 7)
http://support.microsoft.com/kb/308421/en-us
Error Message: "Access Is Denied" When You Try to Open NTFS File System Folders
http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q823306#appliesto