A Dell Inspiron 6000 can only use partitions that are 137GB or smaller. (I can't really explain your 160 GB drive, but maybe it was only using 137 GB of it.) The solution is to put your new hard drive in another computer (e.g., with your 3.5-2.5 adapter), then partition from the other computer. No partition can be larger than 137 GB and all bootable partitions must be within the first 137 GB, I believe.
Maiklas3000, thanks for your answer,
The 160GB hard drive is indeed using all of its available capacity (from memory it comes up as 149GB available) so maybe there are several versions of the Inspiron floating around. Mine is about 4 years old.
Anyway, after a lot of hair pulling, I finally managed to get XP onto the 320GB HDD but it was a long drawn out job:
1/. I installed the original 160GB HDD back in and booted to XP
2/. Connected the 320GB HDD to the laptop via an external case & formatted the drive under XP
3/. Copied a Paragon Drive Backup archive I made of the 160GB HDD with a clean install of XP to the 320GB HDD
4/. Restored the 160GB image to the 320GB HDD and resized the restored partition from 160GB to 320GB
5/. Installed the 320GB HDD back into the laptop
At this stage, XP booted using the 320GB HDD and XP seemed to work fine, showing it now had a new 320GB HDD but after I un-installed a couple of programs that I no longer needed, the laptop re-booted and showed the infamous "Blue Screen of Death". Nothing I did would then make the laptop boot to XP.
I then put the XP Installtion CD in, booted to the CD and started a new installation of XP over the existing installation. Even though this should delete & replace all existing files on the HDD, I was hoping the boot sector may have been changed to allow the new installtion to complete successfully and would be untouched
Anyway, the installation went without a hitch, and I now have the 320GB HDD running fine with a fresh installtion of XP.
It didn't matter before what I did (1 320GB partition, 2 160GB partitions or 3 100GB partitions) once the XP installation files had been copied to the HDD and the system re-booted, it would always show the disc error.
Now that I have a good fresh installation of XP and everything is working, I'll image the disk and use that to do any future re-installations but I really would love to find out why I cant install XP from the CD!!! Any ideas would be greatly appreciated.