Windows on the internal Drive, Gentoo on an external USB Drive

Hi

I tried installing Gentoo 2004.2 on an external USB Drive attached to my laptop. This worked fine up until rebooting after installing the bootloader.
I know the drive recognised as /dev/sda in linux and the partitions on it are:
/dev/sda1 windows ntfs (no OS installed)
/dev/hda2 Extended partition
/dev/sda5 /boot ext3
/dev/sda6 swap
/dev/sda7 /  ext3
the device /dev/hda has only one partition:
/dev/hda1 windows ntfs (windows installed)

I have installed lilo on /dev/hda.
Here's my lilo.conf:

-----
boot=/dev/sda            
           timeout=50                
           default=gentoo            
           vga=788                  
                 
           
           image=/boot/kernel-2.4.26-gentoo-r6
             label=gentoo
             read-only
             root=/dev/ram0
             append="init=/linuxrc ramdisk=8192 real_root=/dev/sda7"
             initrd=/boot/initrd-2.4.26-gentoo-r6
           
           other=/dev/hda1
             label=windows
-----

When i try to boot, its says:
Block device dev/sda is not a valid root device...
The root block device is unspecified or not detected.
please specify a device to boot, of "shell"for a a shell...
After which it asks me for the root partition.

So it seems it cant detect the drive/partition.(i tried to manually enter the root partition, but to no avail)

What do i need to do to make linux boot from the external drive?

Thanks in advance