Dual boot or multiple windows files?

So here is the deal. I have a WD hard drive that I have done a full partition on and will not repartition. I have a second drive that I probably can reinstall windows if need be. I have changed a lot with windows 7 I have added different themes, start orbs, explorer frames/navigation, and system icons. The problem is when my wife gets on it, she hates it. So I made a different user account so that it would be her own look and feel. However the icons and other things are changed in hers also.
So my question is: is there a way to have each user load their own windows explorer.exe and other system32\64 files for each user? Or is there a way that I can have it ask at the begging (much like choosing a user) which drive to boot from? She basically just uses regular standard windows, and I use mine which looks like: http://www.youtube.com/watch?v=vyLcpeioCT8
So the start orb and other folders and file icons transfer to hers as well. I know that she would be happy if there was a way that we could each have different looks. Again I do not want to partition my drive to dual boot. Thanks in advance.