Rainy,
Victor is exactly right. Unfortunately, big programs such as Nero, Roxio and other suites will take over your default viewers much the same way the Windows Media Player with take iTunes and vice versa. Fox and I.E. do the same.
So, you can change the default the way Victor said. Other ways are right clicking on the file and choosing Open With and choose Windows Viewer, etc. If all else fails, there are literally tens to hundreds of free .tiff viewers on the Internet you can Google.
