Stefano, Hmmmm. What I would do next is to trash /Library/Perl. This is where much of where horae goes, though it should be overwritten on installation too. Trashing /Library/Perl is a little riskier than trashing /Applications/Ifeffit because it's possible that some other perl application is using that folder too. If you think you're not using any other perl programs, you probably are not. In any case, you could do sudo mv /Library/Perl /Library/Perl_SAVE You can also look at the list of Perl files installed (at least as of horae-0.48 on Mac 10.3) at http://cars9.uchicago.edu/ifeffit/src/MacOSX/PerlFiles This says 'Perl/5.8.1' everywhere and I believe 10.4 uses a more recent version of perl, but this list be helpful in looking for folders not installed by Ifeffit. After doing this, you can retry the installation. If that's too scary (or doesn't work ;>) I hope Paul has some insight! --Matt