saree

Hello all, i would like to ask for help since i searched for it all over the net and here and i didn't find what i'm looking for. what i would like to do is to install dual operating system in dual partition in the same hard drive XP VISA or XP XP which ever one that will allow me to make each one of them do not see the other OS partition or files. what i did before is that i installed XP first as FAT32 and then i added Vista in the other partition as NTFS but both OS see each other when i log to any one of them. so it didn't work for me. i would like to have these to work to install a one system that will allow the user to log in to our company network that OS should be strictly closed and would not allow the user to change anything on it that OS will be XP. the other OS will allow the user to full control on it that OS will be VISTA or XP any one will do. any way you know now what i require so please let me know any suggestions that will work. i need to do this with out the use of any third party tools but there is no harm to mention that if it's the right way to do it.