[R] How to update R from ver 1.9.1 to 2

[Srinivas Iyyer]

Dear group, 
 apologies if this is a stupid question.  I searched
CRAN sites. I am afraid I missed it.  
Can any one help me if I can update my windows version
of 1.9.1 to 2 or higer. 

thanks
srini