Importing Excel files into R xlsx or xls

Question

Please can someone help me on the best way to import an excel 2007 (.xlsx) file into R. I have tried several methods and none seems to work. I have upgraded to 2.13.1, windows XP, xlsx 0.3.0, I don't know why the error keeps coming up. I tried:

AB<-read.xlsx("C:/AB_DNA_Tag_Numbers.xlsx","DNA_Tag_Numbers")

OR

AB<-read.xlsx("C:/AB_DNA_Tag_Numbers.xlsx",1)

but I get the error:

 Error in .jnew("java/io/FileInputStream", file) : 
  java.io.FileNotFoundException: C:\AB_DNA_Tag_Numbers.xlsx (The system cannot find the file specified)

Thank you.