I have win 7 32 on my desk top I want to change to 64 so I can use all of my memory I have 8gig installed its only reading 3 and my computer is unstable it keeps crashing
More RAM probably won't solve the stability problem. You can't upgrade from 32 to 64 bit. You must do a fresh install of Windows 7 64 bit.
Did you already have Win7 32-bit before you upgraded the RAM to 8GB, or did you already have the 8GB RAM when you installed Win7 32-bit? Just curious... As OtheHill stated, you will have to do a fresh install of Win7 64-bit.
EDIT: I missed this - "want to go back to 64". Apparently you already had the 64-bit version installed? Why did you replace it with 32-bit?