I've got all the Xboxes screwed back together and the server back in place (as is evident from this website working). I ended up getting a Western Digital 320GB HDD (20GB bigger than the old one!) since I read that these run cooler and quieter than all others on the market which I guess means it _should_ last longer (although I've probably just jynxed it). I was quite lucky - they didnt have any Seagates to replace my old one with otherwise I'd have had to accept a straight swap.

All that remains now is to transfer some 141GiB of data back to my storage partition then its all done. You shouldn't notice any significant downtime from now on (maybe just a couple of reboots at most).

Thanks for bearing with me!