what are filename.rar files?
what program must be used?
Winrar, xace, powerarchiver and a variety of other compression and de-compression utilitities will open ans extract rar files.
where can I download them?
you can download winrar here
winrar isn’t free but it is one of the best program around for compressing files
Be sure to check this thread!
As for stuffit, I’m not a real fan of it. WinRAR offers very good compression of most filetypes, and has many extra features such as solid archives, variable dictionary size, volume spanning, authenticity verification, recovery records, recovery volumes, archive locking, passwords, encryption, SFX, the list goes on. (Some features only available to registered users). If you archive a lot WinRAR is a great buy.