I am, or rather was, running iTunes 64 bit on a Win7Pro 64-bit with 8GB memory, and Intel corei7 860 processor.
Problem: itunes will not run or even load. I have gone through the on-line help, uninstalled it and reinstalled it so many times I have lost count, edited the registry as advised and even screamed at it. The last time it even loaded, which it now will not, it told me that the libratry had been created by a later version and could not be opened!
I am running i Tunes ok on W7 64 bit with 2 libraries.Can you say what version of i Tunes yu have - I assume the latest for 64bit? Maybe you could give a bit more detail of the procedure you have used.