XP and Ubuntu as they are on different Partitions. XP can only be installed onto 1 Partition so you have either attempted to install this onto the XP Partition or one of the 3 default Linux Partitions.
I would imagine that you where told something like XP can not find a Hard Drive present and this would be because you have a SATA HDD inside this computer. What you need to do here is make a copy of the SATA Driver for this M'Board and XP and then press the [b]F6 Key[/b] when the first blue screen appears. You then need to insert a floppy with the SATA Driver copied to it's root into the A Drive when prompted and press enter so you can load the SATA Driver.
If you don't have a A Drive available you can use a product like nLite to make a Slipstreamed Install Disc with he SATA Drive included so you do not have to insert a Floppy Disc. It can be downloaded from here
http://tinyurl.com/e2mo4
If you do use nLite make sure that you read the directions available here under Guides
http://tinyurl.com/hh3kb.
Now if this computer had XP and Ubuntu on the one HDD and you want to use the entire HDD to load XP to you need to delete the Partitions for XP & Ubuntu the easiest way to do this is as Old Mycroft said use Boot & Nuke to wipe the HDD. If the different OS's are on different Drives you should wipe both drives and then load Windows onto the Boot Drive and format up the second drive for use under Windows as it can not access Linux Partitions and the space used by Ubuntu will be wasted.
Col