Well, installing W7 on the first partition (primary) didn't make any difference. Still got the same error message.
So, the only thing left was some kind of incompatibility with Grub. I tried "fixmbr" (after booting to the WinXP install disk and choosing Repair) but nothing changed.
Next I tried the following:
Code:
C:\WINDOWS
CD ..
FIXBOOT C:
FIXMBR
BOOTCFG /rebuild
However, even after this the Grub menu still showed up on boot and W7 still wouldn't install for the same reason.
The computer I was using is a spare computer with nothing of importance on it. So, I used Parted Magic to completely delete all partitions. But, even with this, W7 install still gave the same error.
Strangely, when I booted without a CD/DVD in the drive and nothing at all on the HDD, not even a partition, I still got some comments about Grub stage 1.5 and Grub stage 2.
So, it seemed that Grub stage 1 was still in the MBR.
OK, nothing for it now but to use
Code:
dd if=/dev/zero of=/dev/sda bs=512 count=1
to completely remove Grub from the mbr.
And finally, W7 installed
Seems that W7 has some aversion to Grub
However, it's going to have to get used to it as I'm going to re-install both Ubuntu and Windows XP and use Grub (from Ubuntu) in the MBR.