I used one little of each, and I mounted a new hard disk with five partitions:
First Partition (100GB) - Windows Seven: for new Simatic softwares
Second Partition (100GB) - Windows XP: for old simatic softwares, and others that I use, also with Virtual PC with MS-DOS 6.22 for IBS and PCIN 4.2 Softwares. ( I did one cpu to Step 5 too).
Third Partition (20GB) - Windows XP only to Sinumerik operations (HMI Advanced for example).
Fourth Partition (180GB) - Data Partition.
Fifth Partition (100GB) - Recovery Partition (backup).
To this moment I tested all softwares and all right with all..