reco8.0 is the main folder, with all the data from the Febraury 2003 to the December 2007 stored in the data_reco_03.08 folder. 03.08 means that the reconstruction has been done in March 2008, and reflects the state of the calibration used (in this case there were latest time calibration from March 2008).
Different mc_* folders contain reconstructed MC files. The ending represents the runlist used during the reconstruction for efficiency degradation, as explained before. Therefore one need to make sure the usage of correct MC reconstruction during the analysis.
Best of all is to use mc_all, which are most versatile and are done with the runlist of all files from the 01.02.2003 to 31.12.2007. Please refer for the README files in the directory for more explanations of the other folders.
There is a web mirror web_reco of the data disk. It is better to use wget command to download it to the local computer before usage.