Painless way to install a new version of R? - Stack Overflow
"My preferred method on Windows (upgrading 2.10.1 to 2.11.0):
- Install R-2.11.0
- Copy R-2.10.0/library/* to R-2.11.0/library/
- Answer "no" to the prompts asking you if it is okay to overwrite.
- Start R 2.11.0 and then type