Install RStudio from zip file and file association

I decided to give a try to install RStudio from the zip file. The only problem I am seeing is that if I keep multiple versions I would like to reassociate .Rproj files with the newer version of RStudio. It seems that running rstudio.exe do some modifications in the Windows registry. Does any body know how I can change the association of .Rproj with a specific version of RStudio?