Hi and thanks for the answer! Well, I added --auto-ghci-libs after the --add-package (I added it twice since it occurrs in an if-else-statement). However HOpenGL.o still won't built, so I suppose I'll have to do without GHCi (after all I can do the largest part of the project before adding HOpenGL). Did you say that GHCi and HOpenGL works with Linux and Unix however if one adds --auto-ghci-libs ? ( Perhaps I'll install Linux some day then : ) (Guess there is no way to get HOpenGL working with Hugs since it doesn't even work with GHCi ?) Here comes some text from the bulid (perhaps you know what the error is): if test x"" = x ; then \ "/cygdrive/c/Program/Haskell/ghc-5.04/bin/ghc-pkg" --remove-package=HOpenGL | | true ; \ "/cygdrive/c/Program/Haskell/ghc-5.04/bin/ghc-pkg" --add-package --auto-ghci-libs < HOpenGL.conf ; \ else \ "/cygdrive/c/Program/Haskell/ghc-5.04/bin/ghc-pkg" --config-file="" --remove-package=HOpenGL || true ; \ "/cygdrive/c/Program/Haskell/ghc-5.04/bin/ghc-pkg" --config-file="" --force --add-package --auto-ghci-libs < HOpenGL.conf ; \ fi Saving old package config file... done. Writing new package config file... done. Reading package info from stdin... done. Expanding embedded variables...done. building GHCi library `$libdir/HOpenGL.o'...ld: cannot open output file $libdir/HOpenGL.o: No such file or directory done. Saving old package config file... done. Writing new package config file... done. Best regards Magnus Lindberg