如何使用自定义目录位置来安装R包

I am running Rstudio 0.97 with R 3.0.1 on Windows 8.1. I installed a lot of packages through Rstudio and they all went to "\R\R-3.0.1\library". Now I installed R 3.1.0 and set Rstudio to use the new version of R. But then I found the packages are all inaccessible from Rstudio.I am running Rstudio 0.97 with R 3.0.1 on Windo