R 2.6.2 is from 2008. I suggest that you use a more recent version. For very old versions, I think you can use

source("http://bioconductor.org/getBioC.R")

I think also that using install.packages() directly will likely succeed in these very old versions of R / Bioconductor by manually setting the repository URL used in install.packages() to

repos = c("http://www.bioconductor.org/packages/2.1/bioc", 
          "http://cran.r-project.org")
install.packages("Biobase", repos=repos)

This page provides a list of Bioconductor versions associated with R versions.