I vote for WinZip, which I use everyday, because it is very simple and effective: you don´t have to build configuration files or batch jobs, simply click on your folder (in Windows Explorer) and it will suggest you to compress your files to c:\ or to any other place you may want, for example A:
I have a 100Mb IOMEGA internal ZIP drive which you may get for less than $70.00 for the drive, and less than $8.00 each diskette. The rate of compression varies with the kind of information, but you may assume a minimum of 50% and a maximum of 99% reduction, furthermore it compresses full folders, subfolders and files to a single file, which is much more convenient to recognize and keep track of.
For some bucks more you may purchase a second hard drive (or use some discontinued 1 or 2 Gb drive) plus a box called MOBILE RACK (about 15.00) This is in fact two boxes: one goes into an empty 5" bay and should be connected to internal IDE and power supply; the second box allocates your hard drive, then you insert the second box into the first and you have a second drive connected without opening any cabinet, thus you may have as many second boxes with second drives as you want. Myself, installed ALL hard drives this way, so I can take the main drive off and boot a different system. You may find a collection of hard disks in their boxes in my shelves. These devices have made my life easier !
Un abrazo - Andrés