Hello, Although the subject as been discused several times already I could not find the answer to my problem in the list archive so here is the last post (to date) about usb boot problems... After some time I managed to boot on my usb key perfectly (thanks to syslinux!) But I can't boot the brand new key I just got... I think I'm pretty familiar now with the MBR, boot sector and linux boot phases but here my problem is that the BIOS just ignore my key... (I'm using a dell optiplex 170L) On this computer the new key works well under linux but refuses to boot. I tried to boot on an other computer and the new key boots perfectly well On the optiplex I can still boot my old key so there's really a pb between the optiplex and the new key. I saw in syslinux doc that problems could come from geometry settings. So I changed the geometry settings to exactly the ones of the key that works well: it doesn't work. Do you have an idea of what could it come from? I'm also wondering how does the BIOs handles USB devices and what difference it makes to choose HDD, FDD or ZIP USB boot (by the way on the dell BIOS there is no such choice, if the device is found it will be considered as "usb device" and if not, well, it's not found...) Gildas