Maintaining R is not difficult, it simply
requires a few easy steps which will be covered here.
1.) First, find the 'etc' folder in
your R installation. Two examples of where it might be located
are below where x.xx.x refers to the
version number of the R installation you have (e.g. R-2.15.0).
C:\R\R-X.XX.X\etc
C:\Program Files\R\R-X.XX.X\etc
Once inside the 'etc' folder, right-click
on the 'Rprofile.site' file and select "Cut". Now right-click on
your desktop and select "Paste". You do not need to close the
'etc' window/folder.
2.) Second, start R.
3.) Third, click on "Packages" at
the top of the R console and then select "Set CRAN mirror...".
Choose the mirror site you wish to use; it is recommended you
choose a mirror site closest to your physical location -- this
will enable quicker downloading. I generally select USA
(TX 1), which is in Dallas, TX. You can find a list of mirror
site locations at CRAN by clicking
here

4.) Next, click again on "Packages"
in the R console and then select "Select repositories...". By
default, CRAN and CRAN (extras) are selected; I generally also
select R-Forge which contains packages being developed (often
very recent updates to existing packages). Then click the OK
button.
5.) Next, type the following line in
the R console and hit the enter key:
x
<- new.packages()
This line tells R you want to search for
new packages at the repositories selected above and if any are
available, they will be assigned to the object "x". The reason
for doing this is so you can then (once it finishes; it can take
a few minutes), type "x" and hit the return key to see
the names of the new packages; thus allowing you to decide if
you want all of them, some of them, or none of them.
6.) Next, install the new packages
by simply typing the following line in the R console and hit the
enter key:
install.packages(x)
7.) Next, click again on "Packages" in the R console and
then select "Update Packages...". Like with the new packages
command, this can take a few minutes. Once done searching for
updates, you will be presented with a list of updated package,
you can select all of them, some of them, or none of them as you
see fit.
Congratulations, you now have the most up
to date packages.
8.) Now close R and return to the
desktop, cut the 'Rprofile.site' file from the desktop and paste
it back into the 'etc' folder. Close the 'etc' window/folder and
you're on your way.
9.) To determine if a new version of R is
available, simply point your favorite browser to
http://cran.r-project.org/bin/windows/base/