This only applies if you use the Advanced mode in the Sonokinetic Manager. If you use the automated mode of the Sonokinetic Manager to download and extract your purchased product, the process will be automated, leaving you with a fully extracted product folder.
If you prefer to go the direct-download way, for a typical product, there will be an Instruments.rar, an Additionals.rar and multiple Samples.rar files, sometimes split in 16 and 24 bit samples.Of these samples rars open only the first part (.part01) of the archive collections (if 16 and 24 bit you have a part01 for each), the other parts will be extracted automatically. Make sure you don't start the extraction process before your download of all the parts has completely finished.
Free programs we recommend for rar extraction:
on the mac - unrarX
on the PC - 7-zip