Dell Inc. began polling customers about their software preferences on Tuesday as part of an effort by the struggling PC vendor to meet a popular request for desktops and notebooks that run on Linux instead of Windows. Dell posted the survey on a company blog, asking PC users to choose between Linux flavors such as Fedora and Ubuntu, and to pick more general choices such as notebooks versus desktops, high-end models versus value models and telephone-based support versus community-based support.