LDA/PCA and more

Hi!!
I was trying to  analyze my data by doing a linear discriminants and I 
encountered
problems with collinearity.  So I am planning to do a PCA to extract 
orthogonal
components and then analyze them using linear discriminants.  I don't know
 how to relate the orthogonal components back to my real data. Is there some
way I can do this  and are there any methods in R that will help me ?
Many thanks. Cheers ../Murli

-