installing xp error

[soni29]

hi,
I little background, i have a dell xps 400, had windows xp on it, it started having issues, i couldn't locate my xp cd so i installed vista, but i only have the trial version, so i have another week left. i located my xp cd, but it won't install. keeps saying it can't locate the hard drive, i do have a sata drive with the pc. so i tried to locate the drivers for the motherboard, think i found them, put them onto a usb, i don't have a floppy drive. during the install when it asked if i have drivers i hit F6, but i keeps saying it wants to read from my A: drive, but i don't have one. i can't seem to get it to change to look in the usb instead, now after it can't read from a:, i get this message:
your computer's startup program cannot gain access to the disk containing the partition or free space you chose.
i also tried to remove the parition with vista on there and put xp on there, but same error message.

any ideas on how i can get xp back?? otherwise i was thinking about buying vista business, can i use that key with the vista ultimate trail i have installed, will it be able to take the key and just remove ultimate features without needing me to install from start like the xp is.

[glc]

You HAVE to use a floppy drive to install XP. There is no way around it at all. Buy one, borrow one, or pull one out of another machine and temporarily connect it - you don't have to permanently mount it in the case, just let it hang out the side. The other option is borrow or buy a USB floppy drive.

If you did not delete the recovery partition, you can reinstall XP by pressing Ctrl+F11 at startup.