There seems to be a problem when installing SQL server 2008 on a windows 2008 RC2 platform. Generally it will get stuck, hangs at "Install_sql_is_Cpu65_Action:Write_NativeImage_64" or another place about 3/4 the way through the install process. In some cases this may be a permissions issue and others media read/write issue.
Best solution for this is to copy the entire contents of the install media directly to the HDD and run the installer directly from the hard drive as the administrator directly from console and not from RDP. This seems to solve the problem in all cases so far.