ProMass DecView is a windows application that allows you to view results files obtained from ProMass Deconvolution results (.dec) files. ProMass normally produces HTML web pages with embedded static graphic files (mass spectra and chromatograms). These static web page images cannot be zoomed or reconfigured. ProMass DecView allows you to download the deconvoluted spectra directly from your browser into ProMass DecView, where you can zoom, print or export the images in a number of high quality formats. DecView supports viewing of the deconvoluted mass spectra and associated ESI mass spectra. The deconvolution results can be interactively validated by clicking a mass in the deconvoluted spectrum pane to highlight the location of related charge states in the ESI spectrum pane.
There are many ways to open deconvolution results files with ProMass DecView.
An example ProMass report showing a deconvoluted spectrum is shown below. The spectrum can be opened either by double-clicking the graphic, or by clicking on the [View Data] link.
The first time you double-click a spectrum or click the [View Data] link within your browser, you will see a dialog similar to the one shown below:

The dialog indicates that Internet Explorer has recognized the .dec file type and is asking you what you want to do with the file. Click the Open button. If you want Internet Explorer to automatically open this file type from now on without showing this dialog, you should uncheck the Always ask before opening this type of file option.
The deconvoluted spectrum shown above opened in DecView.

For more information about using ProMass DecView, access the ProMass DecView online help.
Configuring Firefox to open deconvolution results (.dec) files
By default Firefox does not automatically open .dec files in DecView. This is because Firefox treats .dec files as plain text by default. You will need to install and configure a Firefox Add-on called Mime Edit to be able to easily open .dec files with Firefox. The Mime Edit Firefox extension can be obtained here:
https://addons.mozilla.org/en-US/firefox/addon/4498