I guess you got a lot of this small .rar files which together constitutes a other file like a movie etc.. just open any one of the .rar file and extract it to the folder same as that of the .rar files..winrar will do the job and extract the whole lot of that thing and you shall have the desired file with you.
Follow these steps and you are done:
You need to download WinRAR - *www.rarlabs.com
Then, I assume your some rars like; .rar .r01 .r02 .r03 etc
Just open the .RAR file and extract the contents, it will automatically extract from the other rars assuming they're all in the same directory.
If you put all the 50 files in one folder, the .rar and the .r01... etc
Then install WinRAR, the icons of the .rar..r01 will change now.
Then just double click on the .RAR file and you will see the movie file in WinRAR - you then just extract this, you don't need to open the .r01.. etc as WinRAR extracts from those automatically.