Question if one buys a HP, Dell or whatever they say home XP is
included. Does that mean the CD is included if not what happens if the
hard disk crashes ?
A CD is included, but it's not the true XP install CD. It's a
"recovery" CD. It will only restore an installed image of XP, as per
factory defaults. If the hard drive itself actually dies, you're
screwed. HP and Compaq (not sure about Dell) puts all the required
drivers, apps, and even certain parts of the OS on a separate
partition on the hard drive. The restore CD won't even work without
that partition and all the data on it intact.
A genuine XP install CD would give you more flexibility, as it allows
you to install the OS cleanly to a new hard drive if you need to
replace it, or to reclaim the space on that restore partition.
I don't know all the policies of the big OEMs, but if the situation
arises, they will sell you a second restore CD containing an image of
the restore partition (usually for something like $10 or $20). If you
push for it, you may also find that there's an option to buy a real
OEM copy of XP. I say "may" because not all OEMs offer such an
option, and those that do, tend to be reluctant about it for whatever
reason.