recent Ubuntu update broke the GRUB loader
 

A friend of mine, who no longer has web access due to being unable to boot, asked me how to fix his Wubi installation.

I'm the guy who suggested he install Ubuntu inside Windows in the first place, thinking that would be the easiest way to get him into Ubuntu. Now, I can't figure out how to repair his grub loader without killing his Windows XP installation.

I'm a Windows guy (have to be, I'm a gamer), so my knowledge of Ubuntu is limited to whatever I can do in the GUI. The command line is beyond me at the moment ('cause it ain't DOS) so I'm very much in need of help with this one. More so because I have an identical installation to his system (I built both), and I'm wondering if this is about to happen to me too.

well that's why is single OS installation recommended for beginners.

besides ubuntu has moved to new version of grub that makes things even more complicated

Considerably more detail would probably be needed before you could get any realistic help. What happened just prior to his being unable to boot? What was he updating? Which bootloader was he using?

Ugh, wubi - which version of Ubuntu (might indicate grub version)?.

Second thoughts, just go back to the XP boot-loader. If you have an XP install disk (any one, not specific to the install) read this technet note. Option 2.

Then go and uninstall wubi, and install Ubuntu in it's own partition (dual boot). Any future boot issues will be a lot easier to fix.