And these days...
Where are the install disks?
Either its on a partition on the already defunct computer or the user was supposed to make a DVD after setting it up for the first time.
Most people, ie the ones that need the help in the first place:
don't make regular backups of their data
don't know where their software install disks if they ever had any
don't know where their licence keys are (probably in an email on their computer)
can't actually remember all the programs they had installed.
have lots of websites with "remember me" ticked and haven't written down their logons (though they probably all use the same password)
have a desktop setup that is like an old friend to them.
In which case getting the ailing PC back into operation sufficiently that these things can be located and backed up before doing a reinstall is worth an attempt if the user/customer is happy with the time it will take.