The files need to have the same format and name in order to open them in order. For this to happen, you also need WinRAR to be installed properly without errors. Visit the official website and download the WinRAR installation package. With a reinstallation you will also fix various problems with files and its functionality. There is, however, the possibility that the files are actually corrupted and recovery with splitted archives is known to fail because things get complicated.
Download WinRAR: http://www.rarlab.com/download.htm