win 7 won't boot up at all, can't reinstall

hi all,
my copy of win 7 was getting increasingly ropey the other week (kept freezing etc.) but i was able to start it in safe mode.
now it won't boot at all, when i try to start it form the hard disc it says 'loading files' with a white bar along the bottom which crawls up, i have left this for hours with no joy.
when i try to reinstall it gets as far as letting me select the language and then just hangs with the busy mouse icon, again i have left for ages with no joy.
so the OS seems to be corrupted and sadly i have files on the OS section of the disc (yes i know....backup!) which i need.

so i assume i somehow need to get another OS to work to back my stuff up and then format the hard disc.

i saw you can in theory run linux from a memory stick, enabling me to back the files up. running xp from a stick is another option which i tried but my laptop didn't seem to boot from it, despite being set to do so.
i have another laptop, aswell as a device which can use a sata/ide hard disc as usb disc, could i maybe remove the hard disc and do this ?

it's an HP 625 laptop with windows 7 32-bit pro.

any help much appreciated.

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