Installing as dual boot with windows

I'm having trouble installing Ubuntu. I've installed 8.10 before as a dual boot on my machine (Windows XP3) on a 120Gb USB hard disk. My system is set up as : First Hard drive, partitioned to give C: (on which I put Windows XP) D: all my data. 2nd Hard drive: E: a 120Gb usb hard drive, partitioned half and half to give space for backups and for Ubuntu. I had a Windows crash a week ago, had to reinstall Windows on Drive C and although the previous version of Ubuntu still existed on the 120 Gb usb drive, I couldn't get the option to boot into it at startup time. I therefore decided to reinstall Ubuntu (9.04), so I used Aesus partitioner to clean off the old 8.10 version. Now, when I use the CD to install 9.04, when I get to the partitioning section, it doesn't show me that I already have Windows XP installed and although I've tried a couple of times to install it on the E:drive (using the choose partitions manually option) it goes through all the right motions, apparently installs, but then won't give me the option to boot into Ubuntu on start up. OK, so I'm doing something stupid, but please, can you tell me what? Thanks.

Boot order

Try changing your boot order in the BIOS.

Windows install does not play nice with any other operating system and will wipe your Ubuntu install along with the GRUB boot loader. It is Grub that gives you the boot options. If you rebuild your C drive with XP you then have to install Ubuntu on C again to get the boot loader. If you don't and just install Ubuntu on drive E, Grub is going to exist only on drive E. When you boot, the BIOS is going to go through the boot order and is going to boot the first operating system it finds - which will be Windows "Drive C". Since Grub is not there, you will not get the boot options.

If you change your boot options in the BIOS and make Drive E boot first (the USB drive), you will get the boot options. Windows might still be missing from the list depending on what you did during the Ubuntu install. In that case you will have to get dirty and change /boot/grub/menu.lst

If you already tried to reinstall Ubuntu on Drive C and Ubuntu did not recognize that XP is already there - well then I am at a loss. I have never heard of the Aesus partitioner. There is only one partitioner that I trust when it comes to Linux and that is GParted.

Choosing Boot loader location

During the Ubuntu install, in Step 7 "Ready to Install", click on the advanced button (at the bottom of screen). A dialog box will open asking you the location of the boot loader to install. I think this will allow you to install Ubuntu on drive D (for e.g) but override the boot loader on drive C.