Start removing the variables one by one until you find out which one is causing the problem. Most likely, you've set HOUDINI_PATH. This is an environment variable that all Houdini installations use. This has nothing to do whether Houdini is re-installed or not.
yes, but the problem is that I did not set any variables and I have nothing to clean. I tried to delete Houdini notes from Windows registry editor after uninstalling, but the part of them are locked.