For your host or your guest? What is your host? I was hoping that you meant to describe the usefullness of that product when I read the topic. However, it seems to be a question - not a description of how you have successfully used something to make Parallels a better product. Perhaps you should read how Parallels chooses to define their forum contents and choose a place where your question would have a better chance of being answered.
I've never used a registry cleaner, because most of them are 3rd party products from obscure web sites, and I would be concerned that they would cause more problems than they would solve. Parallels makes it easy to backup a windoze installation so that if anything bad goes on, you just have to copy a file to recover. It's the 2nd best solution to using a basically insecure OS. The best solution is just to use Linux and let the windoze monoply die out like IBM did long ago.
