title: Switching from InstallShield to WiX
body: <p>I am looking for a replacement for InstallShield. Unfortunately we only have 1 license for InstallShield and it was installed on a developer's machine. I'm considering switching over to WiX, but after reading the documentation there is a Product ID GUID, Upgrade Code GUID and a Package GUID.</p>
  
  <p>I also know GUID's were created by InstallShield. If I switch over to WiX can I start using new GUID's or do I have use some of the GUID's created by InstallShield? If an upgrade to a product is released will switching installers hose customers who had the old installer?</p>