There are lots of reasons that you might have problems.
1) is your XP disc a retail copy? if it came with a PC or is an OEM, it's effectively locked to the machine it was first installed on
2) you need to get all the drivers for the new computer which means that you need to find out what the motherboard and all other peripherals are.
why not research the software you think might not work and see if it can work either natively or in compatibility mode