To eleminate the possibility of errors, you need to convert the application to a version fully compatible with windows XP, like 6.1 or 7.0 (6.02 should do it)
Would version 5.1 work with XP, NI do not gaurantee that. However, I had installed apllications written in version 5.1.1 and worked fine under XP. In your case, just give a try, if it did not work as expected, you may have functuionality that may not be fully comptaible with XP.