[Hampshire] Ubuntu install issue

I've just tried installing Ubuntu 9.04 and am having some issues that
I'm hoping someone can help me out with. I tried to do a clean install
of 9.04 today onto a new disk that I'd already partitioned using (my
still working) 8.10 install as follows:
First 250MB to be used for /boot
Next 20GB to be used for /
Next ~200GB to be used for /home
And final 5GB for swap

When installing 9.04 I selected the manual partition setup and just told
it to use the above partitions. Off it went and did its thing including
detecting that I had XP on another disk. Everything went OK until I
rebooted the system at the end of the install. Ubuntu 9.04 wouldn't boot
and neither would Windows XP. If I select either HDD in the BIOS it just
gets to a screen with a flashing cursor and goes no further. Any ideas
how I can get XP and 9.04 working again?

TIA
Leo

PS Also why was it writing to my XP disk? (At least I presume it was and
that's why it's no longer working)