All my files have been prepared in ver 4. Will they work in new version without any problem. I have 64bit windows.
There is no 64 bit Win XP. Files in the OpenDocument formats edited on one system with one of the release versions should open on any system under any version of Libo. Innovations added to higher versions will, of course, not move to lower versions this way. A Calc file using a standard function first time implemented for V4.4 e.g. will not correctly work under V 3.6.
There is XP64, but it was dead project since its birth (no support and it worked like shit), whereas VI$TA64 was the first working 64-bit Window$.
According to the official site (https://wiki.documentfoundation.org/Feature_Comparison:LibreOffice-_Microsoft_Office), LO 5.1 works on XP.