Getting an older version of a package

Hi there,

Thanks for your time in advance.

I am using an add-on package from Cran. After I updated this package,
some of my programs don't work any more. I was wondering if there is
anything like version control so that I could use the older version of
that package; or if I could manually install the previous version and
how I could acheive it? I am not a regular R user; although it is
supposed to be very easy, after spending many hours on this, I still
haven't figured out how to proceed. Your help will be greatly
appreciated.

CRAN has the older versions of the package available in source form. 
You need to download one of those and install it:  but watch out for 
other packages that depend on the newer one.  In the long run, it's 
probably a better investment of your time to fix your programs to work 
with the new package.  (Or possibly report to the package maintainer if 
they have introduced a bug.)

Prior to R 2.9.0, it was possible to install multiple different versions 
of packages, but this never worked perfectly, and it has been dropped.

Duncan Murdoch