you really didn't provide any details. what exactly are you trying to do with a par file? they are not stand-alone files. they are for repairing a specific broken file that they came with. tell me how many files you downloaded, what type, and how many par p01, etc files came with. you will also need mirror.exe. if you just came across a par someplace and are trying to read it, it will never happen. just delete it.
http://www.codeccorner.com/usenethelp/QuickPar_Primer.html
http://www.the-stables.net/par_files.htm