The SENSwitcher software is enclosed in archives for PC's and Apple Mac's. An archive is a convenient way of storing computer files for delivery across the Internet. It keeps the files intact and also has the added advantage of compressing the files so that they take up less space. In order for you to use them on the computer when you have downloaded the files you need to extract the files into a directory on your own hard drive.
You will then need a de-archiver program to read the files.
There are several pieces of archive software availble on the Internet which will do this for you. Some of these are indicated in the links below.
The SENSwitcher files are just too big to fit on one floppy disc. To enable
the transfer of files to another computer without Internet access the files
have been split to enable two floppies to be used. These files will then
need to be combined again on the machine to enable the software to run successfully.
You will also need 
web plugin for the software to work.
Links to zip archive software
StuffAll (Shareware)
Free Zip Wizard (Freeware)
WinZip (Commercial, although you can downoad an evaluation version) Probably the most widespread software for this format.
Free Zip program (Freeware)
Power Archiver (Freeware)
Stuffit Expander (Freeware) This can also handle Mac archives as well