It could simply be a problem with your computer being able to read/write to HDMCs.

(High-density memory cards)

 Any memory card with a capacity of 8gb or above is generally regarded as being 'high-capacity'.

  Typically, the chips used in these devices are larger and can cause issues with older hardware.

You may wish to check if your hardware supports HDMCs.

  If it does not, you could look for a BIOS update for that motherboard.

Here should be the drivers for that model:

http://support.dell.com/support/downloads/driverslist.aspx?c=us&l=en&s=gen&ServiceTag=&SystemID=LAT_PNT_PM_D400&os=WW1&osl=en&catid=&impid=

Let me know if that helps.

~~rlmax

Does your bios support booting from USB devices?

As far as I can tell  I have the latest bios (A08) - the problem is not to read the usb stick once mounted, but to boot from it.

I can now boot using extlinux, grub really doesn't want to work though... 

Let me guess...it's a Corsair Flash Voyager.

I have a 16GB Flash Voyager that will boot on an XPS420 but will not boot on an M1330 no-way no-how.  Must be the BIOS.

Tom
XPS 420, Q6600, 4GB, 500x2, Radeon HD2600XT, Bluetooth, eSATA, Ultimate SP1
XPS 420, Q6700, 4GB, 750GB x 2 (RAID 0), GeForce 8800 GT, Xcellerator, Bluetooth, eSATA, Ultimate 64-bit SP1
XPS M1330, 2.2GHz, 4GB, 200GB (7200), Vista Ultimate 64-bit SP1
XPS M1330, 2.0GHz, 4GB, 320GB, Quad-Boot: Vista Ultimate 64-bit SP1, XP Pro 64-bit, Ubuntu 8.04 & Media Direct