are you trying to run ./configure from somwhere in MyDocs? That might do this, as fat system doesnt support permissions. try from some other position, like /home/user/
make -C "libstub" all make[1]: Entering directory `/home/martin/Desktop/preenv-0.1.6/libstub' make[1]: Nothing to be done for `all'. make[1]: Leaving directory `/home/martin/Desktop/preenv-0.1.6/libstub' make -C "libpng" all make[1]: Entering directory `/home/martin/Desktop/preenv-0.1.6/libpng' cd "libpng-1.2.44" && ./configure --prefix=/usr /bin/sh: ./configure: Permission denied make[1]: *** [libpng-1.2.44/config.status] Error 126 make[1]: Leaving directory `/home/martin/Desktop/preenv-0.1.6/libpng' make: *** [libpng] Error 2