hp laptop mashed up, what now

hello all,
maybe in here someone can help me out of my mess.
i got the chance to get my fingers on a hp laptop, pavilion , core duo, 2x 1.8Ghz, and .... why not ???
but, then the freedom was over.
it doesn`t accept any other thing than the original hp-restore CD.
no windows-setup CD supports the SATA-hdd in this unit, so i have to setup the xp-home that came with the machine.
ok, no big deal.
but, i made up the laptop with hard work to my pleasure, deleted the backup-partition, as well as some useless software,
resized the C: drive to 20 gb and the rest was goin to be my partition for all the privat data.
but, what can i say: i screwed the system, didn`t read carefully the vista-transformation information, cancelled a setup-dialogue before i should have, and so it crashes.
well; not really.
i still can boot into windows, log in with all users, but:
there is no GUI anymore. no explorer, no task-bar nothing than the plain desktop-background picture.
even in safe-mode.
i startet to try ctrl-alt-delete, and the task-manager would also not start the explorer, coudn`t find it.
so, what can i do ?
i can`t update windows, let`s say to xp prof. - cause it doesn`t accept the
setup cd.
when i restore with the system-cd , it would lead me to the same thing as when i got the dammned thing, one big C: partition and a backup-part.
and i would have to go through the whole process once again.
and, i would loose some of my data on C: as well as on D:

how could i try to get the explorer back into this f....in system?
can anyone give me any good idea what to try ?


edit:
all i can do is use task-manager, to start some applications in the application-folder - this still works,
so i made some backup of some data with an alternative window-manager, to a usb-hdd.
but i don`t want to install the whole thing from scratch,
help plz