Read the first link in my signature. It will explain the process to you.
Not knowing what all you did in the guide - just understand IF you are on Froyo that Valhalla is a 2.3.6 Gingerbread based ROM. If you are on Froyo and want to upgrade to Gingerbread you will need Gingerbread bootloaders.
If you are indeed still on Froyo and rooted - follow the second link in my signature and flash with bootloaders. Then you can use the directions where applicable in the first link to flash the custom ROM in CWM.
If you are on Gingerbread - what you are trying to flash the ROM in is called CWM Recovery. If the text color is blue when you boot into recovery to flash the ROM - that is not CWM Recovery. It is stock android recovery. The text color needs to be orangish red to indicate you have CWM. To have CWM you need a custom kernal. In that case (being rooted and on Gingerbread) use the first link's guide and start where it talks about flashing a custom kernel using SGS Kernel Flasher.
You will know you do not have Gingerbread bootloaders if you flash a Gingerbread based ROM - when you boot your phone and see a rainbow like screen. This means you need Gingerbread bootloaders.
Last edited by lumin30; 22nd April 2012 at 01:36 PM.