3.7 gigs won't fit on a CD. The program most likely will not run off the CD/DVD.
If the program is installed on the PC the only way to regain that space would be to uninstall it. If the files that you want to put on the DVD/CD are the installation files then you can back them up to a cd or dvd and then delete the old files from the PC.
If you only have a CD burner then you would have to put the files on a bunch of CD's. If its one large file thats taking up the 3.7gigs of space then you would want to get a program like 7-Zip, its capable of compressing the files a little and spanning them across several discs. 7-Zip is free http://www.7-zip.org/