I have installed simpleaffy package, then when I try to use it appears an error.

library(simpleaffy)
Loading required package: genefilter
Error: package or namespace load failed for ‘genefilter’ in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]):
there is no package called ‘XML’
Error: package ‘genefilter’ could not be loaded

And when I charge the package genefilter:

library(genefilter)
Error: package or namespace load failed for ‘genefilter’ in loadNamespace(j <- i[[1L]], c(lib.loc, .libPaths()), versionCheck = vI[[j]]):
there is no package called ‘XML’

I don't know how to fix this error

The (repeated) error you get says

there is no package called ‘XML’

Which seems to be a clear indication that you need to install the XML package.