Dual boot doesn't work anymore

[M. Fioretti]

Greetings,

A few weeks ago I put an extra hard disk on a friend's computer (who
knows nothing about software of any sort) and installed Ubuntu KK on
it. It was the default system, in dual boot (which worked) with the
Windows install still present on the original drive.

my friend has used Ubuntu since then and is happy with it. One week
later the install, I visited him again and ran a system update.

Yesterday the friend decided to boot Windows for a Windows-only game
or something that is still there and now "dual boot doesn't work
anymore" ( we couldn't talk more about this over the phone and almost
surely won't have time until sunday for reasons irrelevant here).

Sunday I'll go there and try to fix things back to normal. The
question for the list is simply: 

which specific Ubuntu documentation, blog posts, whatever I should
read _before_ visiting my friend, so that next sunday I go there with
a clear idea of what could have happened and spend as little time as
possible to fix the problem?

Please note that I am NOT looking for generic, dual boot install
tutorials, I know where those are. Consider that everything was fine,
and broke, even if we didn't realize it immediately, only after an
upgrade. What could it be?

Sorry if this message IS a bit vague, but of course, without the PC in
front of me and no clue of what the error message is...

TIA,
	Marco
-- 
Junior High students in Monza build their own Ubuntu computer
http://stop.zona-m.net/node/106