Is the newer machine actually a new one? If so and it was purchased with XP already installed he should be able to call the PC suppliers help line and get assistance. Do you have an example of a program he cannot load?
I haven't bought XP for home yet so probably won't know the answers, but if you give us an idea of the kind of software causing problems, someone may be able to help. Depending what the programs are which don't run, he might be able to call or e-mail the software suppliers.
There are also lots of PC forums. Don't know much about them, but again maybe some-one else does.
Lid