I have a two hard disk system with WInXP on one of them (Disk1) and I planned to install Ubuntu 9.10 on the other (Disk 2; 80 Gig). Using Partition Magic, I formatted an 8 Gig ext3 partition and an 8 Gib blank partition for swap on the first part of Disk2. The remainder was formatted as an NTFS partition. I downloaded and installed Ubuntu 9.10 into the first two partitions which appeared to succeed as planned.
I restarted, Grub appeared and I chose Ubuntu which booted. So far so good. I exited normally and powered down. Later I attempted to restart but got the message "no such disk" and a "grub repair>" prompt.
I then used the WindowsXP recovery manager to fixmbr, fixboot, and one other fix command (I don't remember which).
That allowed me to boot to Windows but now Partition Magic claims all of Disk 2 is bad and can't do anything with it. So how do I fix Disk 2 so it can be used?
I finally discovered that I could disconnect Disk 1, use Windows XP's repair function on the CD to fixmbr and reformat the Linux partition. After reconnecting Disk 1, I then rebooted to XP. Partiton Magic still said "Bad Disk" but XP's own disk manager could see the partitions on disk2. There appeaed to be twice as much space in the partitions as there was on the disk and one partition seemed to be the entire disk. Clicking on it revealed that windows disk mgr couldn't do anything with it but delete it. That I did, and the probelm was solved. Of course, I wonder why the Linux install created this mess in the first place, but that's another issue.