I have a Vostro 1700 here that I am going to have a play with dual drives in it.
Most seem to be ordered with just one drive so in order to fit another hard drive you will need to get a few parts from dell first. Parts required for the second hard drive bay are:
Screws caddy to drive and caddy to bay DLC-XC467 & DLC-XC470
Now I just got onto support and told them I had bought a 2nd drive and was unable to fit it as they didnt supply the kit with the machine, they arranged to send me the parts foc, you may not be so lucky and have to pay.
My Vostro came with 160gb 5400rpm drive in bay 1
I have bought a 100Gb 7200rpm drive for bay 2
It looks very much like you should be able to select in bios which of the 2 drives to boot from and maybe use the boot manager to choose Vista or XP too. This is unknown as yet as I've not got as far as installing XP Pro on the 2nd drive yet.
Maybe something horrid will happen when the machine boots to see a 2nd drive with a MBR and one will get deleted, I'm unsure atm
If thats the case then it still means I can trial XP on the vostro to see if its indeed quicker than Vista, I will just remove one drive.
So this is a bit of a work in progress thread and I welcome any input as I'm sure many of you who just bought stonking Dell deals may be interested in doing something like this too.