Hi 
There is a trick.
Any Ubuntu, even a previous release, can be installed over the top of a
different install without re-formatting. Some settings and configs get
over-written . It can repair a partial or failed install (or upgrade).
If you try a straight install of Ubuntu onto the same partitions, when you get
to the "Partitioning Section" (about 7th or 8th page i think) choose the
"Advanced" / "Manual" or now "Something different" option then you can choose
the Mount Points. Make sure the column "Format?" has no ticks in it.
Afterwards the
/home/user
folder gives a good indication of some of the programs that had been installed
so just open Synaptic to reinstall them
Reformatting will obviously wipe anything on the partition so just make sure the
partitions don't get formatted.
One thing i found amazing about this was a multi-tabs firefox session that i
killed in one release using 1 edition of Firefox successfully re-opened all the
right tabs in a different release of both Ubuntu and firefox! Bookmarks were
all there too but that wasn't so much of a surprise.
Regards from
Tom